Question 1

A medical researcher compared the variances in birth weights for five randomly chosen babies of each gender,with the MegaStat results shown below. The population variances:
A) may be assumed equal at any customary $\alpha$.
B) should be assumed unequal at any customary $\alpha$.
C) are not relevant to this paired t-test.

Accepted Answer

The population variances are not relevant to this paired t-test because the test is comparing the variances of the two groups, not the variances of the individual observations.

Question 2

Does the Speedo Fastskin II Male Hi-Neck Bodyskin competition racing swimsuit improve a swimmer's 200-yard individual medley performance times? A test of 100 randomly chosen male varsity swimmers at several different universities showed that 66 enjoyed improved times,compared with only 54 of 100 female varsity swimmers.To test for equality in the proportions of men versus women who experienced improvement,the test statistic is approximately:
A) 1.73
B) 1.47
C) 2.31
D) Can't tell without knowing the tail of the test.

Accepted Answer

The test statistic is calculated using the formula for comparing two proportions. The result, approximately 1.73, does not depend on the tail of the test (one-tailed or two-tailed) for its calculation, only for its interpretation against a critical value.

Question 3

Random samples of students were compared to see whether or not there was a difference in the proportion favoring the university's proposed switch from MWF (three-day)classes to MW and TR (two-day)classes.The results shown below are from MegaStat.Analyze these results thoroughly.

Accepted Answer

The answer of Random samples of students were compared to...

Question 4

The table below compares two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations.Very briefly,what conclusions can you draw?

Accepted Answer

The answer of The table below compares two samples taken...

Question 5

Which is not a type of comparison for which you would anticipate a two-sample test?
A) Before versus After.
B) Old versus New.
C) Current versus Target.
D) Experimental versus Control.

Accepted Answer

A two-sample test is not appropriate for comparing a current value with a target value because there is no second sample to compare it to. The other choices (Before vs After, Old vs New, Experimental vs Control) involve comparing two separate samples or groups.

Question 6

The coach of an adult Master's Swim class selected eight swimmers within each of the two age groups shown below.A 50-yard freestyle time is recorded for each swimmer.The resulting times (seconds)are shown below.Which statistical test would you choose to compare the two groups?
A) t-test for independent samples with known variances
B) t-test for independent samples with unknown variances
C) t-test for paired samples
D) z-test for two independent proportions

Accepted Answer

The two groups are independent, and their variances are unknown. Therefore, the best choice is to perform a t-test for independent samples with unknown variances.

Question 7

Does the Speedo Fastskin II Male Hi-Neck Bodyskin competition racing swimsuit improve a swimmer's 200-yard individual medley performance times? A test of 100 randomly chosen male varsity swimmers at several different universities showed that 66 enjoyed improved times,compared with only 54 of 100 female varsity swimmers.In comparing the proportions of males versus females,is it safe to assume normality?
A) Yes,clearly.
B) Yes,but just barely.
C) No.
D) Can't tell without knowing $\alpha$.

Accepted Answer

Since the sample size is large enough (100 for both male and female), we can assume normality of the proportions of improved times for both genders. Therefore, it is safe to assume normality.

Question 8

Jason wants to perform a two-tailed test for equality between two independent sample proportions.Each sample has at least 10 "successes" and 10 "failures." Jason's test statistic is -1.44.What is his p-value?
A) .1498
B) .0749
C) .9251
D) Between .01 and .05

Accepted Answer

The answer of Jason wants to perform a two-tailed test...

Question 9

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. What are the critical values for a two-tailed test for equal variances at $\alpha$= .05?
A) 0.275,3.14
B) 0.244,3.37
C) 0.210,3.95
D) 0.181,4.32

Accepted Answer

The answer of The table below shows two samples taken...

Question 10

A medical researcher wondered if there is a significant difference between the mean birth weight of boy and girl babies.She weighed a random sample of five babies of each gender.Their weights (pounds)are shown below,along with some MegaStat results. The population means:
A) may be assumed equal at any customary $\alpha$.
B) should be assumed unequal at any customary $\alpha$.
C) are not relevant to this paired t-test.

Accepted Answer

The population means are not relevant to this paired t-test because the test is comparing the mean difference between the two groups, not the individual means of each group.

Question 11

Random samples of Tuesday and Friday withdrawals from a college-campus ATM were compared to see whether or not there was a difference in the means.The results shown below are from MegaStat.Analyze these results thoroughly.

Accepted Answer

The answer of Random samples of Tuesday and Friday withdrawals...

Question 12

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. At $\alpha$ = .05,can you conclude that the first sample has a larger variance than the second sample?
A) Yes,clearly.
B) Yes,but just barely.
C) No.

Accepted Answer

The answer of The table below shows two samples taken...

Question 13

The z-test for zero difference in two means:
A) is generally the preferred test for means.
B) is rarely suitable for business data.
C) is the most powerful test for means.
D) is not available in Excel's Data Analysis.

Accepted Answer

The z-test for zero difference in two means is rarely suitable for business data because it assumes a known population variance and normally distributed data, conditions that are often not met in business contexts.

Question 14

Group 1 has a mean of 13.4 and group 2 has a mean of 15.2.Both populations are known to have a variance of 9.0 and each sample consists of 18 items.What is the test statistic to test for equality of population means?
A) -1.755
B) -1.643
C) -1.800
D) -1.285

Accepted Answer

The answer of Group 1 has a mean of 13.4...

Question 15

A confidence interval for the difference of two population means:
A) must pool the sample variances.
B) may or may not pool the sample variances.
C) cannot be used to test for equal population means.

Accepted Answer

A confidence interval for the difference of two population means may or may not pool the sample variances depending on whether or not the population variances are assumed to be equal. This is known as the pooled or unpooled variance method. The choice of which method to use depends on whether or not the variances are assumed to be equal, which can be tested using a hypothesis test or based on prior knowledge. Additionally, a confidence interval for the difference of two population means can be used to test for equal population means by checking if the interval contains zero.

Quiz 10: Two-Sample Hypothesis Tests

A medical researcher compared the variances in birth weights for five randomly chosen babies of each gender,with the MegaStat results shown below. The population variances:

Random samples of students were compared to see whether or not there was a difference in the proportion favoring the university's proposed switch from MWF (three-day)classes to MW and TR (two-day)classes.The results shown below are from MegaStat.Analyze these results thoroughly.

The table below compares two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations.Very briefly,what conclusions can you draw?

Which is not a type of comparison for which you would anticipate a two-sample test?

The coach of an adult Master's Swim class selected eight swimmers within each of the two age groups shown below.A 50-yard freestyle time is recorded for each swimmer.The resulting times (seconds) are shown below.Which statistical test would you choose to compare the two groups?

Jason wants to perform a two-tailed test for equality between two independent sample proportions.Each sample has at least 10 "successes" and 10 "failures." Jason's test statistic is -1.44.What is his p-value?

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. What are the critical values for a two-tailed test for equal variances at $\alpha$ = .05?

A medical researcher wondered if there is a significant difference between the mean birth weight of boy and girl babies.She weighed a random sample of five babies of each gender.Their weights (pounds) are shown below,along with some MegaStat results. The population means:

Random samples of Tuesday and Friday withdrawals from a college-campus ATM were compared to see whether or not there was a difference in the means.The results shown below are from MegaStat.Analyze these results thoroughly.

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. At $\alpha$ = .05,can you conclude that the first sample has a larger variance than the second sample?

The z-test for zero difference in two means:

Group 1 has a mean of 13.4 and group 2 has a mean of 15.2.Both populations are known to have a variance of 9.0 and each sample consists of 18 items.What is the test statistic to test for equality of population means?

A confidence interval for the difference of two population means:

Quiz 10: Two-Sample Hypothesis Tests

A medical researcher compared the variances in birth weights for five randomly chosen babies of each gender,with the MegaStat results shown below. The population variances:

Random samples of students were compared to see whether or not there was a difference in the proportion favoring the university's proposed switch from MWF (three-day)classes to MW and TR (two-day)classes.The results shown below are from MegaStat.Analyze these results thoroughly.

The table below compares two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations.Very briefly,what conclusions can you draw?

Which is not a type of comparison for which you would anticipate a two-sample test?

The coach of an adult Master's Swim class selected eight swimmers within each of the two age groups shown below.A 50-yard freestyle time is recorded for each swimmer.The resulting times (seconds) are shown below.Which statistical test would you choose to compare the two groups?

Jason wants to perform a two-tailed test for equality between two independent sample proportions.Each sample has at least 10 "successes" and 10 "failures." Jason's test statistic is -1.44.What is his p-value?

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. What are the critical values for a two-tailed test for equal variances at α\alphaα = .05?

A medical researcher wondered if there is a significant difference between the mean birth weight of boy and girl babies.She weighed a random sample of five babies of each gender.Their weights (pounds) are shown below,along with some MegaStat results. The population means:

Random samples of Tuesday and Friday withdrawals from a college-campus ATM were compared to see whether or not there was a difference in the means.The results shown below are from MegaStat.Analyze these results thoroughly.

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. At α\alphaα = .05,can you conclude that the first sample has a larger variance than the second sample?

The z-test for zero difference in two means:

Group 1 has a mean of 13.4 and group 2 has a mean of 15.2.Both populations are known to have a variance of 9.0 and each sample consists of 18 items.What is the test statistic to test for equality of population means?

A confidence interval for the difference of two population means:

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. What are the critical values for a two-tailed test for equal variances at $\alpha$ = .05?

The table below shows two samples taken to compare the mean age of individuals who purchased the iPhone 3G at two AT&T store locations. At $\alpha$ = .05,can you conclude that the first sample has a larger variance than the second sample?