Question 1

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)N.
D)We cannot tell without knowing α.

Accepted Answer

The answer of Does the Speedo Fastskin II Male Hi-Neck...

Question 2

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 the assumption of equal variances is justified. If the assumption of equal variances is reasonable, then the sample variances can be pooled to increase the sample size and improve the accuracy of the confidence interval. However, if the assumption of equal variances is not reasonable, then the sample variances should not be pooled, and separate intervals should be calculated for each population mean.

Question 3

Which is not a type of comparison for which you would anticipate a two-sample test?
A)Before Treatment versus After Treatment
B)Old Method versus New Method
C)Sample Mean versus Desired Mean
D)Experimental Group versus Control Group

Accepted Answer

Two-sample tests are used to compare two different groups, while comparing a sample mean to a desired mean would only require a one-sample test. Therefore, the option C is not a type of comparison for which you would anticipate a two-sample test.

Question 4

Which Excel function would give the critical value for a left-tailed F test to compare two sample variances?
A)=F.INV(α,df1,df2)
B)=F.DIST(s12/s22,df1,df2)
C)=F.INV(α/2,df1,df2)
D)=1−F.DIST(s12/s22,df1,df2)

Accepted Answer

The function F.INV(α,df1,df2) gives the critical value for a left-tailed F test to compare two sample variances. The parameters df1 and df2 are the degrees of freedom for the numerator and denominator, respectively, and α is the significance level.

Question 5

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 6

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 a.
B)should be assumed unequal at any customary a.
C)are not relevant to this paired t-test.

Accepted Answer

Since the researcher is comparing the variances of birth weights of the two genders, it is appropriate to assume equal variances in the population. Therefore, Option A is the best choice.

Question 7

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 α.
B)should be assumed unequal at any customary α.
C)are not relevant to this paired t-test.

Accepted Answer

The answer of A medical researcher wondered if there is...

Question 8

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 = .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 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 α = .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

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 11

Which Excel function would give a p-value for a left-tailed F test to compare two sample variances?
A)=1−F.DIST(s12/s22,df1,df2)
B)=F.INV(α,df1,df2)
C)=F.DIST(s12/s22,df1,df2)
D)=F.INV(α/2,df1,df2)

Accepted Answer

The F.DIST function is used to calculate the cumulative distribution function (CDF) for the F-test. In this case, we want to find the probability of getting an F-test statistic as extreme or more extreme than the observed value, assuming a left-tailed test. This can be calculated by dividing the smaller sample variance by the larger sample variance (s12/s22) and plugging this value into the F.DIST function, along with the degrees of freedom for the numerator (df1) and denominator (df2). The resulting output will give us the p-value for the test.

Question 12

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)We cannot tell without knowing the tail of the test.

Accepted Answer

We can use a two-sample proportion z-test to test for equality in the proportions of male and female swimmers who experienced improvement in their 200-yard individual medley performance times. The test statistic is calculated as follows:
z = (p₁ - p₂) / sqrt(p̂(1 - p̂) * (1/n₁ + 1/n₂))
where p₁ and p₂ are the sample proportions of swimmers who experienced improvement, p̂ is the pooled proportion, n₁ and n₂ are the sample sizes.
Using the given data, we have:
p̂ = (66 + 54) / (100 + 100) = 0.60
z = (0.66 - 0.54) / sqrt(0.60 * 0.40 * (1/100 + 1/100)) = 1.73
The critical value for a two-tailed test at α = 0.05 is 1.96. Since the calculated test statistic (1.73) is less than the critical value, we fail to reject the null hypothesis and conclude that there is not enough evidence to suggest a difference in the proportion of male versus female swimmers who experienced improvement in their 200-yard individual medley performance times.

Question 13

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 14

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 15

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 16

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

Since the variances are unknown, we would use a t-test for independent samples with unknown variances to compare the two age groups in terms of their 50-yard freestyle times.

Quiz 10: Two-Sample Hypothesis Tests

A confidence interval for the difference of two population means

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

Which Excel function would give the critical value for a left-tailed F test to compare two sample variances?

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 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 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

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 = .05,can you conclude that the first sample has a larger variance than the second sample?

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 = .05?

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 Excel function would give a p-value for a left-tailed F test to compare two sample variances?

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.

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.

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?

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?