Question 1

There is interest at the American Savings and Loan as to whether there is a difference between average daily balances in checking accounts that are joint accounts (two or more members per account)versus single accounts (one member per account).To test this,a random sample of checking accounts was selected with the following results:
  Based upon these data,the critical value from the t-distribution for testing the difference between the two population means using a significance level of 0.05 is t = 1.6772.

Accepted Answer

A) True 
 B)False

Question 2

Assume that you are testing the difference in the means of two independent populations at the 0.05 level of significance.The null hypothesis is: H0 : μA - μβ ≥ 0 and you have found the test statistic is  What should you conclude?

Accepted Answer

A) The mean of pop.A is greater than the mean of pop.B because p-value  α. 
C) There is no significant difference in the two means because p-value > α. 
D) The mean of pop.B is greater than the mean of pop.A because p-value < α.

Question 3

An accounting firm has been hired by a large computer company to determine whether the proportion of accounts receivables with errors in one division (Division 1)exceeds that of the second division (Division 2).The managers believe that such a difference may exist because of the lax standards employed by the first division.To conduct the test,the accounting firm has selected random samples of accounts from each division with the following results.
  Based on this information and using a significance level equal to 0.05,the critical value from the standard normal table is z = 1.645.

Accepted Answer

A) True 
 B)False

Question 4

There are a number of highly touted search engines for finding things of interest on the Internet.Recently,a consumer rating system ranked two search engines ahead of the others.Now,a computer user's magazine wishes to make the final determination regarding which one is actually better at finding particular information.To do this,each search engine was used in an attempt to locate specific information using specified keywords.Both search engines were subjected to 100 queries.Search engine 1 successfully located the information 88 times and search engine 2 located the information 80 times.Using a significance level equal to 0.05,which of the following is true?

Accepted Answer

A) Based the sample data,the null hypothesis of equal population proportions is rejected since the test statistic exceeds the critical value. 
B) Based on the sample data,the null hypothesis should not be rejected since the test statistic of z = 2.04 exceeds the critical value of z = 1.96. 
C) According to the test results,the hypothesis should be rejected since the test statistic value,z = 1.54,falls in the rejection region. 
D) Based on the sample data,there is not sufficient evidence to conclude that a difference exists between the proportion of search hits since the test statistic,z = 1.54,does not fall in the rejection region.

Question 5

If the population variances are assumed to be known in an application where a manager wishes to estimate the difference between two population means,the 95 percent confidence interval estimate can be developed using which of the following critical values?

Accepted Answer

A) z = 1.645 
B) z = 1.96 
C) t value that depends on the sample sizes from the two populations 
D) z = 2.575

Question 6

Descent,Inc. ,produces a variety of climbing and mountaineering equipment.One of its products is a traditional three-strand climbing rope.An important characteristic of any climbing rope is its tensile strength.Descent produces the three-strand rope on two separate production lines: one in Bozeman and the other in Challis.The Bozeman line has recently installed new production equipment.Descent regularly tests the tensile strength of its ropes by randomly selecting ropes from production and subjecting them to various tests.The most recent random sample of ropes,taken after the new equipment was installed at the Bozeman plant,revealed the following:  Descent's production managers are willing to assume that the population of tensile strengths for each plant is approximately normally distributed with equal variances.Based on the sample results,can Descent's managers conclude that there is a difference between the mean tensile strengths of ropes produced in Bozeman and Challis? Conduct the appropriate hypothesis test at the 0.05 level of significance.

Accepted Answer

A) Because the calculated value of t = 0.896 is neither less than the lower tail critical value of t = -2.0167,nor greater than the upper tail critical value of t = 2.0167,do not reject the null hypothesis.Based on these sample data,at the α = 0.05 level of significance there is not sufficient evidence to conclude that the average tensile strength of ropes produced at the two plants is different. 
B) Because the calculated value of t = 0.451 is neither less than the lower tail critical value of t = -2.0167,nor greater than the upper tail critical value of t = 2.0167,do not reject the null hypothesis.Based on these sample data,at the α = 0.05 level of significance there is not sufficient evidence to conclude that the average tensile strength of ropes produced at the two plants is different. 
C) Because the calculated value of t = -2.8126 is less than the lower tail critical value of t = -2.0167,reject the null hypothesis.Based on these sample data,at the α = 0.05 level of significance there is sufficient evidence to conclude that the average tensile strength of ropes produced at the two plants is different. 
D) Because the calculated value of t = 2.8126 is greater than the lower tail critical value of t = -2.0167,reject the null hypothesis.Based on these sample data,at the α = 0.05 level of significance there is sufficient evidence to conclude that the average tensile strength of ropes produced at the two plants is different.

Question 7

Suppose that a group of 10 people join a weight loss program for 3 months.Each person's weight is recorded at the beginning and at the end of the 3-month program.To test whether the weight loss program is effective,the data should be treated as:

Accepted Answer

A) independent samples using the normal distribution. 
B) paired samples using the t-distribution. 
C) independent samples using the t-distribution. 
D) independent proportions.

Question 8

The NCAA is interested in estimating the difference in mean number of daily training hours for men and women athletes on college campuses.It wants 95 percent confidence and will select a sample of 10 men and 10 women for the study.The variances are assumed equal and the populations normally distributed.The sample results are:
  Based on these data,the lower limit for the difference between population means is 0.15 hours.

Accepted Answer

A) True 
 B)False

Question 9

Construct a 95% confidence interval estimate for the difference between two population means based on the following information:

Accepted Answer

A) 25.41 ≤ (µ1 - µ2)≤ 44.59 
B) 35.41 ≤ (µ1 - µ2)≤ 40.59 
C) 15.741 ≤ (µ1 - µ2)≤ 54.16 
D) 22.13 ≤ (µ1 - µ2)≤ 47.87

Question 10

The Sergio Lumber Company manufactures plywood.One step in the process is the one where the veneer is dried by passing through a huge dryer (similar to an oven)where much of the moisture in the veneer is extracted.At the end of this step,samples of veneer are tested for moisture content.It is believed that pine veneer will be less moist on average than will fir veneer.The following data were reported recently where the values represent the percent of moisture in the wood:
  The null and alternative hypotheses to be tested are
H0 : μp ≥ μf
Ha : μp f

Accepted Answer

A) True 
 B)False

Question 11

A direct retailer that sells clothing on the Internet has two distribution centers and wants to determine if there is a difference between the proportion of customer order shipments that contain errors (wrong color,wrong size,etc. ).It takes a sample of orders from each distribution center and obtain the following results:
  Based on these data it can proceed with assuming the normal distribution for each of the proportion sampling distributions.

Accepted Answer

A) True 
 B)False

Question 12

The Sergio Lumber Company manufactures plywood.One step in the process is the one where the veneer is dried by passing through a huge dryer (similar to an oven)where much of the moisture in the veneer is extracted.At the end of this step,samples of veneer are tested for moisture content.It is believed that pine veneer will be less moist on average than will fir veneer.The hypothesis test that will be conducted using an alpha = 0.05 level will be a two-tailed test.

Accepted Answer

A) True 
 B)False

Question 13

The t-distribution can be used to test hypotheses about the difference between two population means given the following two assumptions:
- each population is normally distributed,and
- the two populations have equal variances.

Accepted Answer

A) True 
 B)False

Question 14

Increasing the size of the samples in a study to estimate the difference between two population means will increase the level of confidence that a decision maker can have regarding the interval estimate.

Accepted Answer

A) True 
 B)False

Question 15

A recent study posed the question about whether Japanese managers are more motivated than American managers.A randomly selected sample of each was administered the Sarnoff Survey of Attitudes Toward Life (SSATL),which measures motivation for upward mobility.The SSATL scores are summarized below.  Judging from the way the data were collected,which test would likely be most appropriate?

Accepted Answer

A) Related samples t-test for mean difference 
B) Pooled-variance t-test for the difference in means 
C) Independent samples Z-test for the difference in means 
D) Related samples Z-test for mean difference

Question 16

The test statistic that is used when testing hypotheses about the difference between two population proportions is the t-value from the t-distribution.

Accepted Answer

A) True 
 B)False

Question 17

A major manufacturer of home electronics is interested in determining whether customers have a preference between two new speaker designs for their home entertainment centers.To test this,the design department manager has selected a random sample of customers and shown them the first design.A second sample of customers is shown design 2.The manager then asks each customer whether they prefer the new design they were shown over the one they currently own.The following results were observed:
  Based on these data and a significance level equal to 0.05,the test statistic is approximately -4.22 and thus the null hypothesis should be rejected.

Accepted Answer

A) True 
 B)False

Question 18

The management of the Seaside Golf Club regularly monitors the golfers on its course for speed of play.Suppose a random sample of golfers was taken in 2011 and another random sample of golfers was selected in 2006.The results of the two samples are as follows:  Based on the sample results,can the management of the Seaside Golf Club conclude that average speed of play was different in 2012 than in 2011? Conduct the appropriate hypothesis test at the 0.10 level of significance.Assume that the management of the club is willing to accept the assumption that the populations of playing times for each year are approximately normally distributed with equal variances.

Accepted Answer

A) Because the calculated value of t = -2.03 is less than the lower tail critical value of t = - 1.6686,reject the null hypothesis.Based on these sample data,at the α = 0.10 level of significance there is sufficient evidence to conclude that the average speed of play is different in 2012 than in 2011. 
B) Because the calculated value of t = 1.84 is greater than the upper tail critical value of t = 1.6686,reject the null hypothesis.Based on these sample data,at the α = 0.10 level of significance there is sufficient evidence to conclude that the average speed of play is different in 2012 than in 2011. 
C) Because the calculated value of t = 0.89 is neither less than the lower tail critical value of t = - 1.6686,nor greater than the upper tail critical value of t = 1.6686,do not reject the null hypothesis.Based on these sample data,at the α = 0.10 level of significance there is not sufficient evidence to conclude that the average speed of play is different in 2012 than in 2011. 
D) Because the calculated value of t = 1.17 is neither less than the lower tail critical value of t = - 1.6686,nor greater than the upper tail critical value of t = 1.6686,do not reject the null hypothesis.Based on these sample data,at the α = 0.10 level of significance there is not sufficient evidence to conclude that the average speed of play is different in 2012 than in 2011.

Question 19

To test whether Model A and Model B cars have the same MPG,the first step is to select two independent random samples of drivers and assign one of them to drive Model A and the other Model B.

Accepted Answer

A) True 
 B)False

Question 20

There have been complaints recently from homeowners in the north end claiming that their homes have been assessed at values that are too high compared with other parts of town.They say that the mean increase from last year to this year has been higher in their part of town than elsewhere.To test this,the assessor's office staff plans to select a random sample of north end properties (group 1)and a random sample of properties from other areas within the city (group 2)and perform a hypothesis test.Based on the information provided,the research (or alternate)hypothesis is:

Accepted Answer

A) μ1 = μ2 
B) μ1 ≠ μ2 
C) μ1 > μ2 
D) μ1 2

Exam 10: Estimation and Hypothesis Testing for Two Population Parameters

Assume that you are testing the difference in the means of two independent populations at the 0.05 level of significance.The null hypothesis is: H₀ : μ_A - μ_β≥ 0 and you have found the test statistic is What should you conclude?

If the population variances are assumed to be known in an application where a manager wishes to estimate the difference between two population means,the 95 percent confidence interval estimate can be developed using which of the following critical values?

Suppose that a group of 10 people join a weight loss program for 3 months.Each person's weight is recorded at the beginning and at the end of the 3-month program.To test whether the weight loss program is effective,the data should be treated as:

Construct a 95% confidence interval estimate for the difference between two population means based on the following information:

The t-distribution can be used to test hypotheses about the difference between two population means given the following two assumptions: - each population is normally distributed,and - the two populations have equal variances.

Increasing the size of the samples in a study to estimate the difference between two population means will increase the level of confidence that a decision maker can have regarding the interval estimate.

The test statistic that is used when testing hypotheses about the difference between two population proportions is the t-value from the t-distribution.

To test whether Model A and Model B cars have the same MPG,the first step is to select two independent random samples of drivers and assign one of them to drive Model A and the other Model B.