Week 8: Quiz

Question 1:
If you were constructing a 99% confidence interval of the population mean based on a sample of n = 25 where the standard deviation of the sample S = 0.05, the critical value of t will be:

a. 2.7969
b. 2.7874
c. 2.4922

Question 2:
It is desired to estimate the mean total compensation of CEOs in the Service industry. Data were randomly collected from 18 CEOs and the 95% confidence interval was calculated to be ($2,181,260, $5,836,180). Which of the following interpretations is correct?

a. 95% of the sampled total compensation values fell between $2,181,260 and $5,836,180.
b. We are 95% confident that the mean of the sampled CEOs falls in the interval $2,181,260 to $5,836,180.
c. We are 95% confident that the mean total compensation of all CEOs in the Service industry falls in the interval $2,181,260 to $5,836,180.

Question 3:
Holding the sample size fixed, increasing the level of confidence in a confidence interval will necessarily lead to a wider confidence interval.

a. True
b. False
c. The information is insufficient

Question 4:
An economist is interested in studying the incomes of consumers in a particular country. The population standard deviation is known to be $1,000. A random sample of 50 individuals resulted in a mean income of $15,000. What is the upper end point in a 99% confidence interval for the average?

a. $15,052
b. $15,141
c. $15,364

Question 5:
An economist is interested in studying the incomes of consumers in a particular country. The population standard deviation is known to be $1,000. A random sample of 50 individuals resulted in a mean income of $15,000. What is the width of the 90% confidence interval?

a. $465.23
b. $364.30
c. $232.60

Question 6:
A major department store chain is interested in estimating the mean amount its credit card customers spent on their first visit to the chain’s new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: Mean= $50.50 and S = 20. Assuming the distribution of the amount spent on their first visit is normal, what is the shape of the sampling distribution of the sample mean that will be used to create the desired confidence interval for μ?

a. a normal distribution
b. a Z distribution
c. a t distribution with 14 degrees of freedom

Question 7:
A major department store chain is interested in estimating the mean amount its credit card customers spent on their first visit to the chain’s new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: Mean= $50.50 and S = 20. Construct a 95% confidence interval for the mean amount its credit card customers spent on their first visit to the chain’s new store in the mall assuming that the amount spent follows a normal distribution.

a. $50.50 ± $11.08
b. $50.50 ± $9.09
c. $50.50 ± $11.00

Question 8:
If the mean of a sample is 125 and the standard deviation is 24, what is the 99% confidence interval estimate for the mean of the population if n = 36?

a. 124.68 <= mean <= 155.32
b. 116.68 <= mean <= 145.32
c. 114.68 <= mean <= 135.32

Question 9:
What is the critical value of t for 95% confidence level and n=10?

a. 2.2222
b. 2.2622
c. 2.2922

Question 10:
What should the sample size be for a 95% confidence interval estimation of the population mean to within a sampling error of ±5 and the standard deviation of 15?

a. 32
b. 33
c. 35

Tutorial for Quiz