Exam 11: Inferences About Population Variances

A random sample of 41 scores of students taking the ACT test showed a standard deviation of 8 points.Provide a 98% confidence interval estimate for the standard deviation of all the ACT test scores.

The manager of the service department of a local car dealership has noted that the service times of a sample of 30 new automobiles has a standard deviation of 6 minutes.A 95% confidence interval estimate for the standard deviation of the service times for all their new automobiles is

The chi-square value for a one-tailed (upper tail)hypothesis test at 95% confidence and a sample size of 25 is

A sample of 41 observations yielded a sample standard deviation of 5.If we want to test H₀: $\sigma$ ² = 20,the test statistic is

A sample of 15 items provides a sample mean of 18 and a sample variance of 16.Compute a 95% confidence interval estimate for the standard deviation of the population.

The symbol used for the variance of the population is

We are interested in testing to see if the variance of a population is less than 7.The correct null hypothesis is

A random sample of 25 employees of a local utility firm showed that their monthly incomes had a sample standard deviation of $112.Provide a 90% confidence interval estimate for the standard deviation of the incomes for all the firm's employees.

A sample of 61 items provided a sample mean of 932,a sample mode of 900,and a sample standard deviation of 11.Test the following hypotheses using $\alpha$ = 0.05.What is your conclusion?

Exhibit 11-8 -Refer to Exhibit 11-8.The p-value is

The critical value of F at 95% confidence when there is a sample size of 21 for the sample with the smaller variance,and there is a sample size of 9 for the sample with the larger sample variance is

We are interested in determining whether or not the variances of the starting salaries of accounting majors is significantly different from management majors.The following information was gathered from two samples. At 90% confidence,test to determine whether or not the variances are equal.

Exhibit 11-7 We want to test the hypothesis that population A has a larger variance than population B. -Refer to Exhibit 11-7.The p-value is approximately

Which of the following has an F distribution?

Exhibit 11-4 -Refer to Exhibit 11-4.The test statistic for this problem equals

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6.At 95% confidence,the null hypothesis

A sample of 21 elements is selected to estimate a 90% confidence interval for the variance of the population.The chi-square value(s)to be used for this interval estimation is (are)

Exhibit 11-2 We are interested in determining whether or not the variances of the sales at two music stores (A and B)are equal.A sample of 26 days of sales at store A has a sample standard deviation of 30 while a sample of 16 days of sales from store B has a sample standard deviation of 20. -Refer to Exhibit 11-2.The p-value for this test is

To avoid the problem of not having access to Tables of F distribution with values given for the lower tail,the numerator of the test statistic should be the one with

Exhibit 11-1 Last year,the standard deviation of the ages of the students at UA was 1.8 years.Recently,a sample of 61 students had a standard deviation of 2.1 years.We are interested in testing to see if there has been a significant change in the standard deviation of the ages of the students at UA. -Refer to Exhibit 11-1.The p-value for this test is