Exam 10: Two-Sample Hypothesis Tests

Management of Melodic Kortholt Company compared absenteeism rates in two plants on the third Monday in November.Of Plant A's 800 employees,120 were absent.Of Plant B's 1200 employees,144 were absent.MegaStat's results for a two-tailed test are shown below. The test statistic (shown as z = x.xx)is approximately

The F-test for equality of variances assumes

In a random sample of patient records in Cutter Memorial Hospital,six-month postoperative exams were given in 90 out of 200 prostatectomy patients,while in Paymor Hospital such exams were given in 110 out of 200 cases.In a left-tailed test for equality of proportions,the p-value is

A pooled proportion is calculated by giving each sample proportion an equal weight.

Management of Melodic Kortholt Company compared absenteeism rates in two plants on the third Monday in November.Of Plant A's 800 employees,120 were absent.Of Plant B's 1200 employees,144 were absent.To compare the two proportions,the pooled proportion is

Kate wants to compare two means.Her sample statistics were 1 = 22.7,s12 = 5.4,n1 = 9 and 2 =20.5,s22 = 3.6,n2 = 9 .Assuming equal variances,the pooled variance is

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.

During a test period,an experimental group of 10 vehicles using an 85 percent ethanol-gasoline mixture showed mean CO2 emissions of 240 pounds per 100 miles,with a standard deviation of 20 pounds.A control group of 14 vehicles using regular gasoline showed mean CO2 emissions of 252 pounds per 100 miles with a standard deviation of 15 pounds.A quick comparison of the sample variances suggests that the population variances are

During a test period,an experimental group of 10 vehicles using an 85 percent ethanol-gasoline mixture showed mean CO2 emissions of 667 pounds per 1000 miles,with a standard deviation of 20 pounds.A control group of 14 vehicles using regular gasoline showed mean CO2 emissions of 679 pounds per 1000 miles with a standard deviation of 15 pounds.At α = .05,in a left-tailed test (assuming equal variances)the test statistic is

Litter sizes (number of pups)for randomly chosen dogs from two breeds were compared.The sample data were entered into Excel,and the following results were produced. What is the critical value for a left-tailed test comparing the means at α = 0.05?

In conducting a paired t-test of the difference between two population means,the usual null hypothesis is that the mean of the population of paired differences is zero.

When sample data occur in pairs,an advantage of choosing a paired t-test is that it tends to increase the power of a test,as compared to treating each sample independently.

A new policy of "flex hours" is proposed.Random sampling showed that 28 of 50 female workers favored the change,while 22 of 50 male workers favored the change.Management wonders if there is a difference between the two groups.What is the test statistic to test for a zero difference in the population proportions?

When the variances are known,a test comparing two independent sample means would use the normal distribution.

A confidence interval for the difference of two population means

In a right-tailed test comparing two proportions,the test statistic was zcalc = +1.81.The p-value is

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

A psychology researcher has a theory that predicts women will tend to carry more cash than men.A random sample of Ersatz University students revealed that 16 females had a mean of $22.30 in their wallets with a standard deviation of $3.20,while 16 males had a mean of $17.30 with a standard deviation of $9.60.The researcher's hypothesis would lead us to perform a

Mary did an analysis of acute care variances in samples of occupancy rates at two community hospitals and obtained the following results: Can Mary conclude that the variances are unequal at α = 0.05?

A new policy of "flex hours" is proposed.Random sampling showed that 28 of 50 female workers favored the change,while 22 of 50 male workers favored the change.Management wonders if there is a difference between the two groups.For a test comparing the two proportions,the assumption of normality for the difference of proportions is