The integral of [tex]z[/tex] over [tex]S[/tex] is equal to the sum of the integrals of [tex]z[/tex] over [tex]S_1,S_2,S_3[/tex].
[tex]S_1[/tex]:Parameterize the surface by
[tex]\vec r(u,v)=(9\cos u,9\sin u,v)[/tex]
with [tex]0\le u\le2\pi[/tex] and [tex]0\le v\le9+9\cos u[/tex]. Take the normal vector to [tex]S_1[/tex] to be
[tex]\dfrac{\partial\vec r}{\partial u}\times\dfrac{\partial\vec r}{\partial v}=(9\cos u,9\sin u,0)[/tex]
Then the integral of [tex]z[/tex] over [tex]S_1[/tex] is
[tex]\displaystyle\iint_{S_1}z\,\mathrm dS=\int_0^{2\pi}\int_0^{9+9\cos u}v\|(9\cos u,9\sin u,0)\|\,\mathrm du\,\mathrm dv=\frac{2187\pi}2[/tex]
[tex]S_2[/tex]:Parameterize [tex]S_2[/tex] by
[tex]\vec s(u,v)=(u\cos v,u\sin v,0)[/tex]
with [tex]0\le u\le9[/tex] and [tex]0\le v\le2\pi[/tex]. Since [tex]z=0[/tex], the integral over [tex]S_2[/tex] is also 0.
[tex]S_3[/tex]:Parameterize [tex]S_3[/tex] by
[tex]\vec t(u,v)=(u\cos v,u\sin v,9+u\cos v)[/tex]
with [tex]0\le u\le9[/tex] and [tex]0\le v\le2\pi[/tex]. The normal to [tex]S_3[/tex] is
[tex]\dfrac{\partial\vec t}{\partial u}\times\dfrac{\partial\vec t}{\partial v}=(-u,0,u)[/tex]
so that the integral over [tex]S_3[/tex] is
[tex]\displaystyle\iint_{S_3}z\,\mathrm dS=\int_0^{2\pi}\int_0^9(9+u\cos v)\|(-u,0,u)\|\,\mathrm du\,\mathrm dv=729\sqrt2\,\pi[/tex]
Putting the results together, the integral of [tex]z[/tex] over [tex]S[/tex] is
[tex]\iint_Sz\,\mathrm dS=\boxed{\left(\frac{2187}2+729\sqrt2\right)\pi}[/tex]
The procedure to evaluate this integral begins by evaluating integrals over the three distinct parts of the surface: the side, bottom, and top. Both the side and bottom integrals are zero and the integral over the top can be evaluated using polar coordinates, however, without specified boundaries for the upper bound, we cannot determine the exact result.
Explanation:The task is to evaluate a surface integral over a surface S, which consists of a cylinder, a disk on the bottom, and a plane on the top. The surface integral of a scalar function z over a surface S is computed by taking the antiderivative of the function with respect to both dimensions defining the area. Since S consists of three parts, S1 (the side), S2 (the bottom), and S3 (the top), we must perform this process for each part and sum the results.
The key steps in the procedure are:
Evaluate the integral over S1. Here, the coordinates x and y satisfy the equation x^2 + y^2 = 81, but since z is constant along the side surface of the cylinder, the integral over S1 is zero.Evaluate the integral over S2. Since it lies in the plane z = 0, the integral over the bottom disk S2 is also zero.Evaluate the integral over S3. As z takes the form of z = 9 + x over S3, this integral can be evaluated using polar coordinates and afterward performing an integration, remembering that x = r cos θ in polar coordinatesSumming the results of our calculations on S1, S2, and S3 would yield the final answer. Unfortunately, without the boundaries for the upper bound for the integration, we cannot provide the exact result.
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Leroy and Fred play chess at a club every Wednesday. The probability that Leroy will lose is .3, that he will stalemate is .5, and that he will win is .2. The probability that Fred will lose is .25, that he will stalemate is .4, and that he will win is .35. What is the probability that at least one of them wins on a given Wednesday?
A .55B .07C .45D .48E .62
Answer:
A .55
Step-by-step explanation:
Given that Leroy and Fred play chess at a club every Wednesday. The probability that Leroy will lose is .3, that he will stalemate is .5, and that he will win is .2. The probability that Fred will lose is .25, that he will stalemate is .4, and that he will win is .35.
lose stale win
Leroy 0.3 0.5 0.2
Fred 0.25 0.4 0.35
Probability that atleast one wins = Prob Leroy wins + Prob fred wins - prob both wins
(using addition theorem on probability)
But prob of both winning is 0
Hence required prob = 0.2 + 0.35 = 0.55
Option a is right
Answer:
0.48
Step-by-step explanation:
The equation of a circle is (x + 6)^2 + (y - 4)^2 = 16. The point (-6, 8) is on the circle.
What is the equation of the line that is tangent to the circle at (-6, 8)?
Answer:
y = 8 is the equation of tangent.
Step-by-step explanation:
The equation of the tangent to the circle at (-6,8) is of the form:
y = mx + c
where m is the slope of the tangent and c is the y-intercept.
The point (-6,8) lies on the circle and the tangent line as well.
Hence (-6,8) satisfies the line equation:
8 = m(-6) + c ⇒ c-6m = 8 -------------1
We know that slope of two perpendicular lines are related as:
[tex]m_{1}\times m_{2}=-1[/tex]
At any point on the circle, the normal line at a point is always perpendicular to the tangent line at that point.
Hence :
[tex]m_{normal} \times m_{tangent}=-1[/tex]
We can find the slope of the normal at point (-6,8) as it passes through the centre of the circle (-6,4) by using the two-points formula for slope.
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]
[tex]=\frac{8-4}{-6+6}[/tex]
= ∞
Slope of the normal is infinity and hence slope of tangent is -1/∞ = 0
Hence m=0
Putting m=0 in equation 1 we get:
c = 8
The equation of tangent line at (-6,8) is:
y = 8
Answer:
y = 8
Step-by-step explanation:
The equation of the tangent to the circle at (-6,8) is of the form:
y = mx + c
where m is the slope of the tangent and c is the y-intercept.
The point (-6,8) lies on the circle and the tangent line as well.
Hence (-6,8) satisfies the line equation:
8 = m(-6) + c ⇒ c-6m = 8 -------------1
When obtaining a confidence interval for a population mean in the case of a finite population of size N and a sample size n which is greater than 0.05N, the margin of error is multiplied by the following finite population correction factor:Image for When obtaining a confidence interval for a population mean in the case of a finite population of size N and aFind the 95% confidence interval for the mean of 200 weights if a sample of 32 of those weights yields a mean of 150.6 lb and a standard deviation of 24.4 lb.a. 143.9 lb < µ < 157.3 lbb. 141.4 lb < µ < 159.8 lbc. 142.8 lb < µ < 158.4 lbd. 142.1 lb < µ < 159.1 lb
Answer:
95% Confidence interval for the mean
[tex]142.8 \leq\mu\leq158.4[/tex]
Step-by-step explanation:
We have to calculate a 95% confidence interval for the mean of a finite population.
The error is multiplied by the following finite population correction factor:
[tex]cf=\sqrt{\frac{N-n}{N-1} }[/tex]
The standard deviation can be estimated as
[tex]\sigma=\frac{s}{\sqrt{n}} \sqrt{\frac{N-n}{N-1} } =\frac{24.4}{\sqrt{32} }* \sqrt{\frac{200-32}{200-1} }=3.963[/tex]
The 95% confidence interval has a z value of 1.96, so it becomes:
[tex]M-z*\sigma_c\leq\mu\leq M+z*\sigma_c\\\\150.6-1.96*3.963\leq\mu\leq 150.6+1.96*3.963\\\\ 142.8 \leq\mu\leq 158.4[/tex]
g A coffee-dispensing machine is supposed to deliver eight ounces of liquid into each paper cup, but a consumer believes that the actual mean amount is less. The critical value for z for a one-tailed test with the tail in the left end is minus1.645 and the obtained value is minus1.87. The appropriate decision is ________.
Answer: Reject the eight- ounces claim.
Step-by-step explanation:
For left tailed test , On a normal curve the rejection area lies on the left side of the critical value.
It means that if the observed z-value is less than the critical value then it will fall into the rejection region other wise not.
As per given ,
Objective : A coffee-dispensing machine is supposed to deliver eight ounces of liquid or less.
Then ,
[tex]H_0: \mu=8\\\\H_a: \mu<8[/tex] , since alternative hypothesis is left-tailed thus the test is an left-tailed test.
the critical value for z for a one-tailed test with the tail in the left end is -1.645 and the obtained value is -1.87.
Clearly , -1.87 < -1.645
⇒ -1.87 falls under rejection region.
⇒ Decision : Reject null hypothesis.
i.e. we reject the eight- ounces claim.
The output of an economic system Q, subject to two inputs, such as labor L and capital K, is often modeled by the Cobb-Douglas production function Q=cL^a K^b. When a+b=1, the case is called constant returns to scale. Suppose Q=12,200, a = 1/6, b= 5/6, and c=42. Find the rate of change of capital with respect to labor, dK/dL.
Answer:
Step-by-step explanation:
Given
Economic system Q is given by
[tex]Q=cL^aK^b[/tex]
also [tex]a+b=1[/tex]
if [tex]Q=12,200[/tex]
[tex]a=\frac{1}{6}[/tex]
[tex]b=\frac{5}{6}[/tex]
[tex]c=42[/tex]
substitute these values
[tex]12,200=42\times (L)^{\frac{1}{6}}K^{\frac{5}{6}}[/tex]
[tex](L)^{\frac{1}{6}}K^{\frac{5}{6}}=\frac{12,200}{42}[/tex]
[tex]K^{\frac{5}{6}}=\frac{12,200}{42(L)^{\frac{1}{6}}}[/tex]
[tex]K=(\frac{12,200}{42})^{\frac{6}{5}}\times \frac{1}{L^{5}}[/tex]
differentiate w.r.t to L to get [tex]\frac{dK}{dL}[/tex]
[tex]\frac{dK}{dL}=(\frac{12,200}{42})^{\frac{6}{5}}\times (-5)\times L^{-6}[/tex]
[tex]\frac{dK}{dL}=-5(\frac{12,200}{42})^{\frac{6}{5}}\times \frac{1}{L^6}[/tex]
[tex]\frac{dK}{dL}=-\frac{4515.466}{L^6}[/tex]
Suppose that administrators at a large urban high school want to gain a better understanding of the prevalence of bullying within their school. They select a random sample of 200 students who are asked to complete a survey anonymously. Of these students, 63 report that they have experienced bullying. Use this information to find a 90% z-confidence interval for p, the true proportion of students at this school who have experienced bullying. Give the limits (bounds) of the confidence interval as a proportion, precise to three decimal places.
lower limit =______________
upper limit =___________
Answer:
lower limit =0.261
upper limit =0.369
Step-by-step explanation:
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
Description in words of the parameter p
[tex]p[/tex] represent the real population proportion of people that have experienced bullying
X= 63 people in the random sample that have experienced bullying
n=200 is the sample size required
[tex]\hat p=\frac{63}{200}=0.315[/tex] represent the estimated proportion of people that have experienced bullying
[tex]z_{\alpha/2}[/tex] represent the critical value for the margin of error
The population proportion have the following distribution
[tex]p \sim N(p,\sqrt{\frac{p(1-p)}{n}})[/tex]
Numerical estimate for p
In order to estimate a proportion we use this formula:
[tex]\hat p =\frac{X}{n}[/tex] where X represent the number of people with a characteristic and n the total sample size selected.
[tex]\hat p=\frac{63}{200}=0.315[/tex] represent the estimated proportion of people that they were planning to pursue a graduate degree
Confidence interval
The confidence interval for a proportion is given by this formula
[tex]\hat p \pm z_{\alpha/2} \sqrt{\frac{\hat p(1-\hat p)}{n}}[/tex]
For the 90% confidence interval the value of [tex]\alpha=1-0.90=0.1[/tex] and [tex]\alpha/2=0.05[/tex], with that value we can find the quantile required for the interval in the normal standard distribution.
[tex]z_{\alpha/2}=1.64[/tex]
And replacing into the confidence interval formula we got:
[tex]0.315 - 1.64 \sqrt{\frac{0.315(1-0.315)}{200}}=0.261[/tex]
[tex]0.315 - 1.64 \sqrt{\frac{0.315(1-0.315)}{200}}=0.369[/tex]
And the 90% confidence interval would be given (0.261;0.369).
We are confident at 90% that the true proportion of people that they were planning to pursue a graduate degree is between (0.261;0.369).
lower limit =0.261
upper limit =0.369
The lower limit of the confidence interval is 0.270, and the upper limit is 0.360.
Explanation:To find the 90% z-confidence interval for the true proportion of students who have experienced bullying, we can use the formula:
CI = p ± z * sqrt((p(1-p))/n)
Where:
p is the sample proportion (63/200 = 0.315)
z is the z-value for a 90% confidence interval (z = 1.645)
n is the sample size (200)
Plugging in these values, we get:
CI = 0.315 ± 1.645 * sqrt((0.315(1-0.315))/200)
Simplifying the equation gives us:
CI = 0.315 ± 0.045
So, the lower limit of the confidence interval is 0.315 - 0.045 = 0.270, and the upper limit is 0.315 + 0.045 = 0.360.
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A chef needs vinegar with an 8% acidity level to make her special sauerbraten. She only has two types of vinegar, one with an acidity level of 5% and the other with 12% acidity level. How many ounces of the 12% vinegar should she add to 40 ounces of the 5% vinegar to obtain the needed vinegar with an 8% acidity level
Answer:
She should add 30 ounces of the 12% vinegar she should add to 40 ounces of the 5% vinegar to obtain the needed vinegar with an 8% acidity level.
Step-by-step explanation:
Let X be ounces of the 12% vinegar she should add to 40 ounces of the 5% vinegar to obtain the needed vinegar with an 8% acidity level.
We have the equation
[tex]\frac{(X*0.12)+(40*0.05}{X+40} =0.08[/tex] when 8% acidity level is reached.
Solving the equation we have
X*0.12+2=0.08(X+40)=0.08X+3.2
That is 0.12X-0.08X=3.2-2=1.2
Finally 0.04X=1.2 and
X=30
The electricity rates charged by Monroe Utilities in the summer months are as follows: Base Charge = $ 8 $8 First 800 800 kWh or less at $ 0.05 $0.05/kWh Over 800 800 kWh at $ 0.08 $0.08/kWh The base is a fixed monthly charge, independent of the kWh (kilowatt-hours) used during the month. a . a. Find an expression for the cost function C ( x ) C(x) for usage of or under 800 800 kWh.
Answer:
[tex]C(x) = \$8 + \$0.05*x[/tex]
Step-by-step explanation:
Let 'x' be the usage in kWh. When usage is at or under 800 kWh, the cost function C(x) is given by the base charge of $8 added to the rate of $0.05/kWh multiplied by the consumption 'x', in kWh.
Therefore, for 0 ≤ x ≤ 800, the cost function is:
[tex]C(x) = \$8 + \$0.05*x[/tex]
Emma's square patio below has been area=31 sq ft. She decides to decrease one dimension by 1 foot and decreases the other dimension by 4 feet. DO NOT USE DECIMAL APPROXIMATIONS. What are the dimensions?
Answer:
4.57ft by 1.57 ft
Step-by-step explanation:
We are given that
Emma's square patio has been area=31 sq.ft
One dimension decrease by 1 foot and other dimension decrease by 4 feet.
We have to find the new dimensions of Emma's patio.
Let x be the side of Emma's square patio
We know that
Area of square=[tex]x^2[/tex]
[tex]x^2=31[/tex]
[tex]x=\sqrt{31}=5.57[/tex] ft
One dimension=[tex]5.57-1=4.57[/tex] ft
other dimension=[tex]5.57-4=1.57 ft [/tex]
Hence, the new dimension of Emma's patio is given by
4.57ft by 1.57 ft
Suppose a package delivery company purchased 14 trucks at the same time. Five trucks were purchased from manufacturer A, four from manufacturer B, and five from manufacturer C. The cost of maintaining each truck was recorded. The company used ANOVA to test if the mean maintenance costs of the trucks from each manufacturer were equal. To apply the F test, how many degrees of freedom must be in the denominator?
Answer:
14
Step-by-step explanation:
Given that a package delivery company purchased 14 trucks at the same time. Five trucks were purchased from manufacturer A, four from manufacturer B, and five from manufacturer C. The cost of maintaining each truck was recorded.
No of companies = 3
No of items in total = 14
Total df = 17-1=16
degrees of freedom between groups = 3-1 =2
Hence degrees of freedom for denominator
=[tex]16-2 =14[/tex]
Suppose that a random sample of 10 newborns had an average weight of 7.25 pounds and sample standard deviation of 2 pounds. a. Test the hypothesis that the average birthweights have decreased at a 5% significance level. Report the p-value of the test. b. Test the hypothesis that the variance of the birth weights have increased at a 1% significance level.
Answer:
[tex]z=\frac{7.25-7.5}{\frac{1.4}{\sqrt{10}}}=-0.565[/tex]
[tex]p_v =P(Z<-0.565)=0.286[/tex]
a) If we compare the p value and the significance level given [tex]\alpha=0.05[/tex] we see that [tex]p_v>\alpha[/tex] so we can conclude that we have enough evidence to FAIL to reject the null hypothesis, so we can conclude that the true average is not significantly less than 7.5.
b) [tex]\chi^2 =\frac{10-1}{1.96} 4 =18.367[/tex]
[tex]p_v =P(\chi^2 >18.367)=0.0311[/tex]
If we compare the p value and the significance level provided we see that [tex]p_v >\alpha[/tex] so on this case we have enough evidence in order to FAIL reject the null hypothesis at the significance level provided. And that means that the population variance is not significantly higher than 1.96.
Step-by-step explanation:
Assuming this info: "Suppose birth weights follow a normal distribution with mean 7.5 pounds and standard deviation 1.4 pounds"
1) Data given and notation
[tex]\bar X=7.25[/tex] represent the sample mean
[tex]s=1.2[/tex] represent the sample standard deviation
[tex]\sigma=1.4[/tex] represent the population standard deviation
[tex]n=10[/tex] sample size
[tex]\mu_o =7.5[/tex] represent the value that we want to test
[tex]\alpha=0.05,0.01[/tex] represent the significance level for the hypothesis test.
z would represent the statistic (variable of interest)
[tex]p_v[/tex] represent the p value for the test (variable of interest)
2) State the null and alternative hypotheses.
We need to conduct a hypothesis in order to check if the true mean is less than 7.5, the system of hypothesis would be:
Null hypothesis:[tex]\mu \geq 7.5[/tex]
Alternative hypothesis:[tex]\mu < 7.5[/tex]
Since we know the population deviation, is better apply a z test to compare the actual mean to the reference value, and the statistic is given by:
[tex]z=\frac{\bar X-\mu_o}{\frac{\sigma}{\sqrt{n}}}[/tex] (1)
z-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".
3) Calculate the statistic
We can replace in formula (1) the info given like this:
[tex]z=\frac{7.25-7.5}{\frac{1.4}{\sqrt{10}}}=-0.565[/tex]
4)P-value
Since is a left tailed test the p value would be:
[tex]p_v =P(Z<-0.565)=0.286[/tex]
5) Conclusion
Part a
If we compare the p value and the significance level given [tex]\alpha=0.05[/tex] we see that [tex]p_v>\alpha[/tex] so we can conclude that we have enough evidence to FAIL to reject the null hypothesis, so we can conclude that the true average is not significantly less than 7.5.
Part b
A chi-square test is "used to test if the variance of a population is equal to a specified value. This test can be either a two-sided test or a one-sided test. The two-sided version tests against the alternative that the true variance is either less than or greater than the specified value"
[tex]n=10[/tex] represent the sample size
[tex]\alpha=0.01[/tex] represent the confidence level
[tex]s^2 =4 [/tex] represent the sample variance obtained
[tex]\sigma^2_0 =1.96[/tex] represent the value that we want to test
Null and alternative hypothesis
On this case we want to check if the population variance increase, so the system of hypothesis would be:
Null Hypothesis: [tex]\sigma^2 \leq 1.96[/tex]
Alternative hypothesis: [tex]\sigma^2 >1.96[/tex]
Calculate the statistic
For this test we can use the following statistic:
[tex]\chi^2 =\frac{n-1}{\sigma^2_0} s^2[/tex]
And this statistic is distributed chi square with n-1 degrees of freedom. We have eveything to replace.
[tex]\chi^2 =\frac{10-1}{1.96} 4 =18.367[/tex]
Calculate the p value
In order to calculate the p value we need to have in count the degrees of freedom , on this case 9. And since is a right tailed test the p value would be given by:
[tex]p_v =P(\chi^2 >18.367)=0.0311[/tex]
In order to find the p value we can use the following code in excel:
"=1-CHISQ.DIST(18.367,9,TRUE)"
Conclusion
If we compare the p value and the significance level provided we see that [tex]p_v >\alpha[/tex] so on this case we have enough evidence in order to FAIL reject the null hypothesis at the significance level provided. And that means that the population variance is not significantly higher than 1.96.
In a large Introductory Statistics lecture hall, the professor reports that 55% of the students enrolled have never taken a Calculus course, 32% have taken only one semester of Calculus, and the rest have taken two or more semesters of Calculus. The professor randomly assigns students to groups of three to work on a project for the course. What is the probability that the first groupmate you meet has studied
a) two or more semesters of Calculus?
b) some Calculus?
c) no more than one semester of Calculus?
Answer:
a) There is a 13% probability that a student has taken 2 or more semesters of Calculus.
b) 45% probability that a student has taken some calculus.
c) 87% probability that a student has taken no more than one semester of calculus.
Step-by-step explanation:
We have these following probabilities:
A 55% that a student hast never taken a Calculus course.
A 32% probability that a student has taken one semester of a Calculus course.
A 100-(55+32) = 13% probability that a student has taken 2 or more semesters of Calculus.
a) two or more semesters of Calculus?
There is a 13% probability that a student has taken 2 or more semesters of Calculus.
b) some Calculus?
At least one semester.
So there is a 32+13 = 45% probability that a student has taken some calculus.
c) no more than one semester of Calculus?
At most one semester.
So 55+32 = 87% probability that a student has taken no more than one semester of calculus.
The correct probabilities for the given scenarios are:
a) The probability that the first groupmate you meet has studied two or more semesters of Calculus is [tex]$\boxed{\frac{13}{100}}$[/tex].
b) The probability that the first groupmate you meet has studied some Calculus (which includes those who have taken only one semester and those who have taken two or more semesters) is [tex]$\boxed{\frac{45}{100}}$[/tex].
c) The probability that the first groupmate you meet has studied no more than one semester of Calculus is [tex]$\boxed{\frac{32}{100}}$[/tex].
To calculate these probabilities, we use the information provided by the professor:
- 55% of the students have never taken a Calculus course.
- 32% have taken only one semester of Calculus.
- The rest, which is 100% - (55% + 32%) = 13%, have taken two or more semesters of Calculus.
Now, let's calculate the probabilities for each part of the question:
a) The probability that the first groupmate has studied two or more semesters of Calculus is the percentage of students who have taken two or more semesters, which is 13%. In probability terms, this is [tex]$\frac{13}{100}$[/tex]
b) The probability that the first groupmate has studied some Calculus is the sum of the percentages of students who have taken at least one semester of Calculus. This includes both those who have taken only one semester (32%) and those who have taken two or more semesters (13%). Therefore, the probability is 32% + 13% = 45%. In probability terms, this is [tex]$\frac{45}{100}$[/tex].
c) The probability that the first groupmate has studied no more than one semester of Calculus is the sum of the percentages of students who have never taken Calculus and those who have taken only one semester. This is 55% + 32% = 87%. However, since we are looking for the probability of no more than one semester, we exclude those who have taken two or more semesters, so we subtract the 13% from the 87%, giving us 87% - 13% = 74%. But this calculation is incorrect because we have double-counted the 32% of students who have taken only one semester. The correct calculation is to consider only the students who have never taken Calculus (55%) and those who have taken only one semester (32%), which gives us 55% + 32% - 0% (since we do not need to subtract any percentage this time) = 87%. In probability terms, this is [tex]$\frac{32}{100}$[/tex], as we are only considering those who have taken no Calculus or just one semester.
Do SAT coaching classes work? Do they help students to improve their test scores? Four students were selected randomly from all of the students that completed an SAT coaching class. For each student, we recorded their first SAT score (before the coaching class) and their second SAT score (after the coaching class).
Student
1
2
3
4
First SAT score
920
830
960
910
Second SAT score
1010
800
1000
980
To analyze these data, we should use
A.
the one-sample t test., one answer Yahoo,
B.
the matched pairs t test.
C.
the two-sample t test.
D.) Any of the above are valid. It just needs to be a t since ? is unknown.
Answer:
B. the matched pairs t test.
Step-by-step explanation:
A paired t-test is used to compare two population means where you have two samples in which observations in one sample can be paired with observations in the other sample. For example if we have Before-and-after observations (This problem) we can use it.
Let put some notation
x=first test value , y = second test value
x: 920, 830, 960, 910
y: 1010, 800, 1000, 980
The system of hypothesis for this case are:
Null hypothesis: [tex]\mu_y- \mu_x \leq 0[/tex]
Alternative hypothesis: [tex]\mu_y -\mu_x >0[/tex]
The first step is calculate the difference [tex]d_i=y_i-x_i[/tex] and we obtain this:
d: 90, -30, 40, 70
The second step is calculate the mean difference
[tex]\bar d= \frac{\sum_{i=1}^n d_i}{n}= \frac{170}{4}=42.5[/tex]
The third step would be calculate the standard deviation for the differences, and we got:
[tex]s_d =\frac{\sum_{i=1}^n (d_i -\bar d)^2}{n-1} =52.520[/tex]
The 4 step is calculate the statistic given by :
[tex]t=\frac{\bar d -0}{\frac{s_d}{\sqrt{n}}}=\frac{42.5 -0}{\frac{52.520}{\sqrt{4}}}=1.618[/tex]
The next step is calculate the degrees of freedom given by:
[tex]df=n-1=4-1=3[/tex]
Now we can calculate the p value, since we have a right tailed test the p value is given by:
[tex]p_v =P(t_{(3)}>1.618) =0.1024[/tex]
So the p value is higher than any significance level assumed (0.05), so then we can conclude that we reject the null hypothesis. So we can conclude that the difference between the after and the initial score it's not significantly higher at 5% of significance.
Solve the following system of equations by the substitution method. 3x = y + 6 x = 2y - 1
Answer:
[tex]x=\frac{13}{5}, y= \frac{9}{5}[/tex]
Step-by-step explanation:
First Equation:
3x = y + 6
Or,
y = 3x - 6
2nd Equation:
x = 2y - 1
Lets substitute the expression for "y" from 1st equation in 2nd and solve for x:
x = 2y - 1
x = 2(3x - 6) - 1
x = 6x - 12 - 1
x = 6x - 13
5x = 13
x = 13/5
Now we can substitute this value of x into bold 1st equation and get y:
y = 3x - 6
y = 3(13/5) - 6
y = 9/5
This is the solution
A sample of 60 items from population 1 has a sample variance of 8 while a sample of 40 items from population 2 has a sample variance of 10. If we test whether the variances of the two populations are equal, the test statistic will have a value of
a. 0.8
b. 1.56
c. 1.5
d. 1.25
Answer: a. 0.8
Step-by-step explanation:
When we test whether the variances of the two populations are equal we use F- test.
Test statistic : [tex]F=\dfrac{s_1^2}{s_2^2}[/tex]
, where [tex]s_1^2[/tex]= sample variance from population 1.
[tex]s_2^2[/tex]= sample variance from population 2.
As per given , we have
[tex]s_1^2=8[/tex] and [tex]s_2^2=10[/tex]
Then, If we test whether the variances of the two populations are equal, the test statistic will be [tex]F=\dfrac{8}{10}=0.8[/tex]
Hence, the test statistic will have a value of 0.8 .
Thus , the correct answer is a. 0.8 .
The manager of a pizza chain in Albuquerque, New Mexico, wants to determine the average size of their advertised 16-inch pizzas. She takes a random sample of 25 pizzas and records their mean and standard deviation as 16.10 inches and 1.8 inches, respectively. She subsequently computes a 95% confidence interval of the mean size of all pizzas as [15.36, 16.84]. However, she finds this interval to be too broad to implement quality control and decides to reestimate the mean based on a bigger sample. Using the standard deviation estimate of 1.8 from her earlier analysis, how large a sample must she take if she wants the margin of error to be under 0.5 inch?
Answer:
n=50
Step-by-step explanation:
1) Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
[tex]\bar X=16.10[/tex] represent the sample mean for the sample
[tex]\mu[/tex] population mean (variable of interest)
s=1.8 represent the sample standard deviation
n=25 represent the sample size
2) Solution to the problem
The confidence interval for the mean is given by the following formula:
[tex]\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}[/tex] (1)
We need to find the degrees of freedom given by:
[tex]df=n-1=25-1=24[/tex]
Since the Confidence is 0.95 or 95%, the value of [tex]\alpha=0.05[/tex] and [tex]\alpha/2 =0.025[/tex], and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.025,0,1)".And we see that [tex]z_{\alpha/2}=\pm 1.96[/tex]
Since we assume that we are taking a bigger sample then we can replace the t distribution with the normal standard distribution, and we can assume that th population deviation is 1.8. The margin of error is given by this formula:
[tex] ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}[/tex] (a)
And on this case we have that ME =0.5 and we are interested in order to find the value of n, if we solve n from equation (a) we got:
[tex]n=(\frac{z_{\alpha/2} \sigma}{ME})^2[/tex] (b)
Replacing into formula (b) we got:
[tex]n=(\frac{1.96(1.8)}{0.5})^2 =49.79 \approx 50[/tex]
So the answer for this case would be n=50 rounded up to the nearest integer
The following information was obtained from matched samples. Individual Method 1 Method 2 1 7 5 2 5 9 3 6 8 4 7 7 5 5 6 Refer to Exhibit 10-5. If the null hypothesis is tested at the 5% level, the null hypothesis _____.
a. should be rejected
b. should be revised
c. should not be rejected
d. None of these answers are correct
Answer:
[tex]p_v =2*P(t_{(8)}<-1.195)=0.266[/tex]
c. should not be rejected
Step-by-step explanation:
1) Data given and notation
The data given is:
Method 1 : 7,5,6,7,5
Method 2: 5,9,8,7,6
[tex]\bar X_{1}=6[/tex] represent the mean for the method 1
[tex]\bar X_{2}=7[/tex] represent the mean for the method 2
[tex]s_{1}=1[/tex] represent the sample standard deviation for the method 1
[tex]s_{2}=1.58[/tex] represent the sample standard deviation for the method 2
[tex]n_{1}=5[/tex] sample size selected for the Consultant A
[tex]n_{2}=5[/tex] sample size selected for the Consultant B
[tex]\alpha=0.05[/tex] represent the significance level for the hypothesis test.
t would represent the statistic (variable of interest)
[tex]p_v[/tex] represent the p value for the test (variable of interest)
State the null and alternative hypotheses.
We need to conduct a hypothesis in order to check if the mean for the difference is equal to 0, the system of hypothesis would be:
Null hypothesis:[tex]\mu_{1}- \mu_{2}=0[/tex]
Alternative hypothesis:[tex]\mu_{1} - \mu_{2}\neq 0[/tex]
If we analyze the size for the samples both are less than 30 so for this case is better apply a t test to compare means, and the statistic is given by:
[tex]t=\frac{\bar X_{1}-\bar X_{2}}{\sqrt{\frac{s^2_{1}}{n_{1}}+\frac{s^2_{2}}{n_{2}}}}[/tex] (1)
t-test: "Is used to compare group means. Is one of the most common tests and is used to determine whether the means of two groups are equal to each other".
Calculate the statistic
We can replace in formula (1) the info given like this:
[tex]t=\frac{6-7}{\sqrt{\frac{1^2}{5}+\frac{1.58^2}{5}}}=-1.195[/tex] (1)
P-value
The first step is calculate the degrees of freedom, on this case:
[tex]df=n_{1}+n_{2}-2=5+5-2=8[/tex]
Since is a two sided test the p value would be:
[tex]p_v =2*P(t_{(8)}<-1.195)=0.266[/tex]
Conclusion
If we compare the p value and the significance level given [tex]\alpha=0.05[/tex] we see that [tex]p_v>\alpha[/tex] so we can conclude that we have enough evidence to FAIL to reject the null hypothesis. So the best option would be:
c. should not be rejected
A sample of 41 observations is selected from one population with a population standard deviation of 3.4. The sample mean is 100.0. A sample of 45 observations is selected from a second population with a population standard deviation of 5.6. The sample mean is 98.4. Conduct the following test of hypothesis using the 0.05 significance level. H0 : μ1 = μ2 H1 : μ1 ≠ μ2
a. One or two tail?
b. State the decision rule. The decision rule is to reject H0 if z is (Outside, Inside) the interval (____,____).
c. Compute value of Test statistic.
d. Reject or Do not reject?
e. what is the p value?
Answer:
a) If we see the alternative hypothesis we see that we are conducting a bilateral test or two tail.
b) (-1.9886, 1.9886)
c) [tex]t=\frac{(100 -98.4)-(0)}{\sqrt{\frac{3.4^2}{41}}+\frac{5.6^2}{45}}=1.617[/tex]
d) [tex]p_v =2*P(t_{84}>1.617) =0.1096[/tex]
So with the p value obtained and using the significance level given [tex]\alpha=0.05[/tex] we have [tex]p_v>\alpha[/tex] so we can conclude that we have enough evidence to FAIL to reject the null hypothesis, and we can said that at 5% of significance the mean of the group 1 is NOT significantly different than the mean for the group 2.
e) [tex]p_v =2*P(t_{84}>1.617) =0.1096[/tex]
We can use the following excel code to calculate it: "=2*(1-T.DIST(1.617;84;TRUE))"
Step-by-step explanation:
The system of hypothesis on this case are:
Null hypothesis: [tex]\mu_1 = \mu_2[/tex]
Alternative hypothesis: [tex]\mu_1 \neq \mu_2[/tex]
Or equivalently:
Null hypothesis: [tex]\mu_1 - \mu_2 = 0[/tex]
Alternative hypothesis: [tex]\mu_1 -\mu_2\neq 0[/tex]
Our notation on this case :
[tex]n_1 =41[/tex] represent the sample size for group 1
[tex]n_2 =45[/tex] represent the sample size for group 2
[tex]\bar X_1 =100[/tex] represent the sample mean for the group 1
[tex]\bar X_2 =98.4[/tex] represent the sample mean for the group 2
[tex]s_1=3.4[/tex] represent the sample standard deviation for group 1
[tex]s_2=5.6[/tex] represent the sample standard deviation for group 2
Part a
If we see the alternative hypothesis we see that we are conducting a bilateral test or two tail.
Part b
On this case since the significance level is 0.05 and we are conducting a bilateral test we have two critical values, and we need on each tail of the distribution [tex]\alpha/2 = 0.025[/tex] of the area.
The distribution on this cas since we don't know the population deviation for both samples is the t distribution with [tex]df=n_1+n_2 -2= 41+45-2=84[/tex] degrees of freedom.
We can use the following excel codes in order to find the critical values:
"=T.INV(0.025,84)", "=T.INV(1-0.025,84)"
And we got: (-1.9886, 1.9886)
Part c
The statistic is given by this formula:
[tex]t=\frac{(\bar X_1 -\bar X_2)-(\mu_{1}-\mu_2)}{\sqrt{\frac{s^2_1}{n_1}}+\frac{S^2_2}{n_2}}[/tex]
And now we can calculate the statistic:
[tex]t=\frac{(100 -98.4)-(0)}{\sqrt{\frac{3.4^2}{41}}+\frac{5.6^2}{45}}=1.617[/tex]
The degrees of freedom are given by:
[tex]df=41+45-2=84[/tex]
Part d
And now we can calculate the p value using the altenative hypothesis:
[tex]p_v =2*P(t_{84}>1.617) =0.1096[/tex]
So with the p value obtained and using the significance level given [tex]\alpha=0.05[/tex] we have [tex]p_v>\alpha[/tex] so we can conclude that we have enough evidence to FAIL to reject the null hypothesis, and we can said that at 5% of significance the mean of the group 1 is NOT significantly different than the mean for the group 2.
Part e
[tex]p_v =2*P(t_{84}>1.617) =0.1096[/tex]
We can use the following excel code to calculate it: "=2*(1-T.DIST(1.617;84;TRUE))"
Consider two populations for which μ1 = 31, σ1 = 3, μ2 = 29, and σ2 = 2. Suppose that two independent random samples of sizes n1 = 4 and n2 = 53 are selected. Describe the approximate sampling distribution of x1 − x2 (center, spread, and shape).a. What is the mean of the distribution?b. What is the standard deviation of the distribution?
Answer:
Part (a): The mean of the distribution is 2.
Part (b): The standard deviation of the distribution is 1.525
Step-by-step explanation:
Consider the provided information.
Part (a) What is the mean of the distribution?
The mean of the sampling distribution of [tex](\bar x_1 -\bar x_2)[/tex] is (µ₁ − µ₂).
It is given that μ₁ = 31, σ₁ = 3, μ₂ = 29, and σ₂ = 2.
Mean of distribution = (x₁ - x₂)
Mean of distribution = (31 - 29) = 2
Hence, the mean of the distribution is 2.
Part (b) What is the standard deviation of the distribution?
If the two samples are independent, the standard deviation of the sampling distribution is: [tex]\sigma_{(x_1-x_2)}=\sqrt{\left(\dfrac{\sigma^2_1}{n_1}+\dfrac{\sigma^2_2}{n_2}\right)}}[/tex]
Substitute the respective values in the above formula.
[tex]\sigma_{(x_1-x_2)}=\sqrt{\left(\dfrac{3^2}{4}+\dfrac{2^2}{53}\right)}}[/tex]
[tex]\sigma_{(x_1-x_2)}=\sqrt{\left(\dfrac{9}{4}+\dfrac{4}{53}\right)}}[/tex]
[tex]\sigma_{(x_1-x_2)}\approx1.525[/tex]
Hence, the standard deviation of the distribution is 1.525
The approximate sampling distribution of x1 - x2 has a mean equal to μ1 - μ2 and a standard deviation equal to √((σ1^2/n1) + (σ2^2/n2)).
Explanation:A sampling distribution is the probability distribution of a statistic, like the mean or proportion, calculated from multiple samples of the same size drawn from a population. It provides insights into the variability of the statistic and is fundamental in statistical inference.
The approximate sampling distribution of x1 - x2 has a mean equal to the difference of the population means, μ1 - μ2. The standard deviation of the distribution is equal to the square root of the sum of the variances of the two populations divided by their respective sample sizes, √((σ1^2/n1) + (σ2^2/n2)).
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The National Center for Education Statistics reported that 47% of college students work to pay for tuition and living expenses. Assume that a sample of 450 college students was used in the study. a. Provide a 95% confidence interval for the population proportion of college students who work to pay for tuition and living expenses (to 4 decimals).
Provide a 99% confidence interval for the population proportion of college students who work to pay for tuition and living expenses (to 4 decimals).
The 95% confidence interval for the population proportion of college students who work to pay for tuition is (0.4228, 0.5172) and the 99% confidence interval is (0.4086, 0.5314).
Explanation:To calculate a confidence interval for a population proportion, we use the formula p ± Z*(√((p(1-p))/n)), where p is the sample proportion, Z is the Z-score associated with our desired confidence level, and n is the sample size.
In this case, p = 0.47 (47%), n = 450, and the Z-scores are 1.96 for a 95% confidence interval and 2.58 for a 99% confidence interval.
For the 95% confidence interval, we calculate:
0.47 ± 1.96*(√((0.47*(1-0.47))/450)) = 0.47 ± 0.0472, so the 95% confidence interval is (0.4228, 0.5172).
For the 99% confidence interval, we calculate:
0.47 ± 2.58*(√((0.47*(1-0.47))/450)) = 0.47 ± 0.0614, so the 99% confidence interval is (0.4086, 0.5314).
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A differential equation of the form y prime (t )equalsF(y) is said to be autonomous (the function F depends only on y). The constant function yequals y 0 is an equilibrium solution of the equation provided Upper F (y 0 )equals0 (because then y prime (t )equals0, and the solution remains constant for all t). Note that equilibrium solutions correspond to horizontal line segments in the direction field. Note also that for autonomous equations, the direction field is independent of t. Consider the equation y prime (t )equals3 sine y .
a. Find all equilibrium solutions in the interva
Answer:
y=n*pi, where n is an integer.
Step-by-step explanation:
We have the equation:
[tex]y'(t)=3sin(y)[/tex]
Which is autonomous because the independent variable does not appear explicitly.
Now, we are asked about all the equilibrium solutions for such autonomous equation. Let's remember that the solution equilibrium y=y0 when F(y0)=0.
Then, matching the given equation to zero, we have:
[tex]y'(t)=3sin(y)=0[/tex]
Which is fulfilled when the sine function has a value of zero. The sine function is worth zero in y=n*pi where n is an integer.
The producer of a certain bottling equipment claims that the variance of all its filled bottles is .027 or less. A sample of 30 bottles showed a standard deviation of .2. The p-value for the test is _____.
a. .025
b. between .025 and .05
c. .05
d. between .05 and .01
Answer:
[tex]p_v = P(\chi^2_{29}>42.963)=1-0.954=0.0459[/tex]
b. between .025 and .05
Step-by-step explanation:
Previous concepts and notation
The chi-square test is used to check if the standard deviation of a population is equal to a specified value. We can conduct the test "two-sided test or a one-sided test".
[tex]\bar X [/tex] represent the sample mean
n = 30 sample size
s= 0.2 represent the sample deviation
[tex]\sigma_o =\sqrt{0.027}=0.164[/tex] the value that we want to test
[tex]p_v [/tex] represent the p value for the test
t represent the statistic
[tex]\alpha=[/tex] significance level
State the null and alternative hypothesis
On this case we want to check if the population standard deviation is less than 0.027, so the system of hypothesis are:
H0: [tex]\sigma \leq 0.027[/tex]
H1: [tex]\sigma >0.027[/tex]
In order to check the hypothesis we need to calculate the statistic given by the following formula:
[tex] t=(n-1) [\frac{s}{\sigma_o}]^2 [/tex]
This statistic have a Chi Square distribution distribution with n-1 degrees of freedom.
What is the value of your test statistic?
Now we have everything to replace into the formula for the statistic and we got:
[tex] t=(30-1) [\frac{0.2}{0.164}]^2 =42.963[/tex]
What is the approximate p-value of the test?
The degrees of freedom are given by:
[tex] df=n-1= 30-1=29[/tex]
For this case since we have a right tailed test the p value is given by:
[tex]p_v = P(\chi^2_{29}>42.963)=1-0.954=0.0459[/tex]
And the best option would be:
b. between .025 and .05
How are the degrees of freedom computed for each test listed below?(a) a chi-square goodness-of-fit test df = k − 1 df = N − 1 df = n − 1 df = (n1 − 1)(n2 − 1) df = (k1 − 1)(k2 − 1)(b) a chi-square test for independence df = k − 1 df = n − 1 df = N − 1 df = (k1 − 1)(k2 − 1) df = (n1 − 1)(n2 − 1)
Answer:
a) [tex]df= k-1[/tex]
b) [tex]df= (k_1-1)(k_2-1)[/tex]
Step-by-step explanation:
Previous concepts
A chi-square goodness of fit test "determines if a sample data matches a population".
A chi-square test for independence "compares two variables in a contingency table to see if they are related. In a more general sense, it tests to see whether distributions of categorical variables differ from each another".
Solution to the problem
Let's define some notation:
N= Total number of individuals for a population
n = Total of individuals selected from a sample
n1= number of objects/individuals with characteristic 1
n2= number of objects/individuals with characteristic 2
k1= number of levels for the variable or factor 1
k2= number of levels for the variable or factor 2
Part a
For a chi square goodness of fit test the degrees of freedom are given by:
[tex]df= k-1[/tex]
Where k represent the total number of categories on the godness of fit test.
Part b
For a chi square test of independence the degrees of freedom are given by:
[tex]df= (k_1-1)(k_2-1)[/tex]
Where k1= number of levels for the variable or factor 1, k2= number of levels for the variable or factor 2 for the chi square test for independence.
In statistical analysis, degrees of freedom (df) are calculated differently based on the type of test. For a chi-square goodness-of-fit test, df equals the number of categories minus one. For a chi-square test for independence, df equals the product of subtracting one from the number of columns and rows.
Explanation:The degrees of freedom (df) play an important role in many statistical tests, including the chi-square tests for goodness-of-fit and independence. These degrees of freedom are calculated differently based on the type of test. In a chi-square goodness-of-fit test, the degrees of freedom is calculated as df = k - 1, where k represents the number of categories or groups in the dataset.
On the other hand, for a chi-square test for independence, the degrees of freedom are calculated using the formula df = (number of columns - 1)(number of rows - 1), where columns and rows represent the different categories or groups present in a contingency table used in the test of independence. In this context, the null hypothesis for this test states that the two factors being considered are independent.
It's important to remember that degrees of freedom often represent the quantity of the 'free' or varying elements in your dataset and directly impact the test results and conclusions. So, having an accurate calculation is crucial in your statistical analysis.
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A curve in polar coordinates is given by: r=9+3cosθ. Point P is at θ=21π/18 .?
a. Find polar coordinate r for P , with r>0 and π<θ<3π/2 .
b. Find Cartesian coordinates for point P.
c. How may times does the curve pass through the origin when 0<θ<2π?
Answer:
Step-by-step explanation:
Given that a curve in polar coordinates is given by:
r=9+3cosθ
a) At point P, we have
[tex]θ=\frac{21\pi}{18}[/tex]
Substitute to get
[tex]r=9+cos \frac{21\pi}{18}\\=9.3932[/tex]
b) Cartesian coordinate is
[tex]x= rcos \theta=3.6934\\y =r sin \tjeta =8.6365[/tex]
c) At the origin r =0
when r =0
we have
[tex]9+3cos\theta=0\\cos\theta =-3[/tex]
Since cos cannot take values as -3 it doe snot pass through origin.
In summary, the polar coordinate r for point P is approximately 9.59. The Cartesian coordinates of P are approximately (0.99, -9.43). The given curve passes through the origin twice in the interval 0<θ<2π.
Explanation:This question is about a curve in polar coordinates. The curve is given by r=9+3cosθ. Let's explore the three sub-questions in order:
a. Find polar coordinate r for P
Because Point P is at θ=21π/18, we can plug this into the equation r=9+3cosθ. This gives r = 9 + 3cos(21π/18) = 9.59.
b. Find Cartesian coordinates for point P.
To convert from polar to Cartesian coordinates, we use the equations x = rcosθ and y = rsinθ. Plugging in our values, we get x = 9.59cos(21π/18) and y = 9.59sin(21π/18). Calculating these gives us x approximately equal to 0.99 and y approximately equal to -9.43. So the Cartesian coordinates for point P are (0.99, -9.43).
c. How many times does the curve pass through the origin when 0<θ<2π?
The curve reaches the origin when r is 0. From the curve equation r = 9 + 3cosθ = 0, we can see the curve crosses the origin twice, at θ = 2π/3 and θ = 4π/3.
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The marginal cost of manufacturing an item when x thousand items are produced is dC/dx= 4x^3 - 6x + 5 dolars/item.Find the cost function C(x) if C(0)=550
Answer:
The cost function is [tex]C(x)=x^4-3x^2+5x+550[/tex].
Step-by-step explanation:
It is given that the marginal cost of manufacturing an item when x thousand items are produced is
[tex]\frac{dC}{dx}=4x^3-6x+5[/tex]
We need to find the cost function.
Multiply both sides by dx.
[tex]dC=(4x^3-6x+5)dx[/tex]
Integrate both sides to find the cost function.
[tex]\int dC=\int (4x^3-6x+5)dx[/tex]
[tex]\int dC=4\int x^3dx-6\int xdx+5\int 1 dx[/tex]
[tex]C(x)=4(\frac{x^4}{4})-6(\frac{x^2}{2})+5x+C[/tex]
where, C(x) is const function and C is a constant.
[tex]C(x)=x^4-3x^2+5x+C[/tex]
It is given that C(0)=550. Substitute x=0 in the above function.
[tex]C(0)=(0)^4-3(0)^2+5(0)+C[/tex]
[tex]C(0)=C[/tex]
[tex]550=C[/tex]
Therefore, the cost function is [tex]C(x)=x^4-3x^2+5x+550[/tex].
The time to fly between New York City and Chicago is uniformly distributed with a minimum of 120 minutes and a maximum of 150 minutes. What is the distribution's standard deviation? Select one: a. 8.66 minutes b. 75 minutes c. 135 minutes d. 270 minutes
Answer:
a. 8.66 minutes
Step-by-step explanation:
Since the flight times are uniformly distributed, the standard deviation can be calculated as follows:
[tex]\sigma = \frac{b-a}{\sqrt{12}}[/tex]
Where 'b' is the maximum flight time (150 minutes) and 'a' is the minimum flight time (120 minutes):
[tex]\sigma = \frac{150-120}{\sqrt{12}}\\\sigma = 8.66\ minutes[/tex]
The distribution's standard deviation is 8.66 minutes.
A manufacturer of salad dressings uses machines to dispense liquid ingredients into bottles that move along a filling line.
The machine that dispenses dressing is working properly when 8 ounces are dispensed. The standard deviation of the process is 0.15 ounces.
A sample of 48 bottles is selected periodically, and the filling line is stopped if there is evidence that the mean amount dispensed is different from 8 ounces.
Suppose that the mean amount dispensed in a particular sample of 48 bottles is 7.983 ounces.
Calculate the P-Value.
Answer:
P-value = 0.4324
Step-by-step explanation:
We are given the following in the question:
Population mean, μ = 8 ounces
Sample mean, [tex]\bar{x}[/tex] = 7.983 ounces
Sample size, n = 48
Population standard deviation, σ = 0.15 ounces
First, we design the null and the alternate hypothesis
[tex]H_{0}: \mu = 8\text{ ounces}\\H_A: \mu \neq 8\text{ ounces}[/tex]
We use Two-tailed z test to perform this hypothesis.
Formula:
[tex]z_{stat} = \displaystyle\frac{\bar{x} - \mu}{\frac{\sigma}{\sqrt{n}} }[/tex]
Putting all the values, we have
[tex]z_{stat} = \displaystyle\frac{7.983 - 8}{\frac{0.15}{\sqrt{48}} } = -0.7851[/tex]
Now, we calculate the p-value with the help of standard normal z table.
P-value = 0.4324
Final answer:
To calculate the P-Value, we need to perform a hypothesis test. The test statistic is calculated by subtracting the hypothesized mean from the sample mean and dividing by the standard error. The P-Value is the probability of observing a test statistic as extreme as the calculated value or more extreme under the null hypothesis.
Explanation:
To calculate the P-Value, we need to perform a hypothesis test. The null hypothesis, H0, is that the mean amount dispensed is equal to 8 ounces, while the alternative hypothesis, Ha, is that the mean amount dispensed is different from 8 ounces.
Using the given information, we can calculate the test statistic, which is the standardized value of the sample mean. First, we calculate the standard error of the sample mean, which is the standard deviation divided by the square root of the sample size. In this case, the standard error is 0.15 / sqrt(48) = 0.021.
The test statistic is then calculated by subtracting the hypothesized mean (8 ounces) from the sample mean (7.983 ounces) and dividing by the standard error. So, the test statistic is (7.983 - 8) / 0.021 = -0.619.
To calculate the P-Value, we need to find the probability of observing a test statistic as extreme as -0.619 (or more extreme) under the null hypothesis. We can use a standard normal distribution table or a calculator to find the corresponding area under the curve. From the table or calculator, we find that the area to the left of -0.619 is 0.269.
Since the alternative hypothesis is two-sided (the mean could be either greater or less than 8 ounces), we double the area to get the P-Value. So, the P-Value is 2 * 0.269 = 0.538.
In a recent survey, 80% of the community favored building a police substation in their neighborhood. If 15 citizens are chosen, what is the mean number favoring the substation?
Answer:
The mean number favoring the substation is 12 citizens.
Step-by-step explanation:
For each citizen surveyed, there are only two possible outcomes. EIther they favored building a police substation in their neighborhood, or they opposed. This means that we use the binomial probability distribution to solve this problem.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, with p probability, and X can only have two outcomes.
Has an expected value of:
[tex]E(X) = np[/tex]
In this problem, we have that:
[tex]n = 15, p = 0.8[/tex]
E(X) = 15*0.8 = 12.
The mean number favoring the substation is 12 citizens.
Final answer:
The mean number of citizens out of 15 who favor the construction of a police substation is 12, calculated by multiplying the sample size (15) by the probability of favoring the substation (0.80).
Explanation:
To find the mean number favoring the substation, we'll use the probability of a citizen favoring the substation to calculate the expected value in a sample of 15 citizens. Since 80% of the community favored building a police substation, the mean number favoring the substation can be computed by multiplying the sample size by the probability of favoring the substation.
Mean = Sample Size × Probability of Favoring the Substation
Mean = 15 × 0.80
Mean = 12
Therefore, the mean number of citizens out of 15 who favor the construction of the police substation is 12.
For a field trip the school bought 39 sandwiches for 4.35 each and 42 bags of chips for 15 cent each how much did the school spend in all
Answer:
Step-by-step explanation:
For a field trip, the school bought 39 sandwiches and 42 bags of chips. Each sandwich cost 4.35. That means the cost of 39 sandwiches would be
39 × 4.35 = 169.65
Each bag of chip costs 15 cents. Converting 15 cents to dollars, it becomes
15/100 =$ 0.15
Therefore, the cost of 42 bags of chips would be
42 × 0.15 = 6.3
Total cost of 39 sandwiches and 42 bags of chips would be
169.65 + 6.3 = 175.95
You want to test your newly created Web site, so you have 250 people access it from random locations at random times. Of the people accessing the site, 75 of them experience computer crashes. You want to estimate the proportion of crashes within a margin of error of 4% at a 95% confidence interval. What sample size do you need?
Answer: 505
Step-by-step explanation:
The formula to find the sample size n , if the prior estimate of the population proportion (p) is known:
[tex]n= p(1-p)(\dfrac{z}{E})^2[/tex] , where E= margin of error and z = Critical z-value.
Let p be the population proportion of crashes.
Prior sample size = 250
No. of people experience computer crashes = 75
Prior proportion of crashes [tex]p=\dfrac{75}{250}=0.3[/tex]
E= 0.04
From z-table , the z-value corresponding to 95% confidence interval = z=1.96
Required sample size will be :
[tex]n=0.3(1-0.3)(\dfrac{1.96}{0.04})^2[/tex] (Substitute all the values in the above formula)
[tex]n= (0.21)(49)^2= 0.21\times2401[/tex]
[tex]n= 504.21\approx505[/tex] (Rounded to the next integer.)
∴ Required sample size = 505