Exam 11: Inferences About Population Variances

Do the following data indicate that the variance of the population from which this sample has been drawn is significantly more than 17? Use $\alpha$ = 0.05.

The bottler of a certain soft drink claims their equipment to be accurate and that the variance of all filled bottles is 0.05 or less.The null hypothesis in a test to confirm the claim would be written as

The grades of a sample of 5 students,selected from a large population,are given below. a.Determine a point estimate for the variance of the population. b.Determine a 95% confidence interval for the variance of the population. c.At 90% confidence,test to determine if the variance of the population is less than or equal to 50.

The sampling distribution of the ratio of independent sample variances extracted from two normal populations with equal variances is the

The standard deviation of the daily temperatures in Honolulu last year was 4 degrees Fahrenheit.A random sample of 25 days resulted in a standard deviation of 5.8 degrees Fahrenheit.Has there been a significant increase in the variance of the temperatures? Use $\alpha$ = 0.05.

A random sample of 31 charge sales showed a sample standard deviation of $50.A 90% confidence interval estimate of the population standard deviation is

The president of a bank believes that the variance of the deposits of suburban customers is more than the variance of city customers.Below you are given the results of samples taken from suburban and city customers. a.State the null and alternative hypotheses to be tested. b.Compute the test statistic. c.Determine the p-value. d.At 95% confidence,what do you conclude?

The standard deviation of the ages of a sample of 16 executives from the northern states was 8.2 years;while the standard deviation of the ages of a sample of 25 executives from the southern states was 12.8 years.At $\alpha$ = 0.1,test to see if there is any difference in the standard deviations of the ages of all the northern and southern executives.

The manager of the service department of a local car dealership has noted that the service times of a sample of 15 new automobiles has a standard deviation of 4 minutes.A 95% confidence interval estimate for the variance of service times for all their new automobiles is

We are interested in testing whether the variance of a population is significantly less than 1.44.The null hypothesis for this test is

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.At 95% confidence the null hypothesis

The chi-square values (for interval estimation)for a sample size of 21 at 95% confidence are

A sample of 60 items from population 1 has a sample variance of 8 while a sample of 40 items from population 2 has a sample variance of 10.If we test whether the variances of the two populations are equal,the test statistic will have a value of

Exhibit 11-5 -Refer to Exhibit 11-5.The null hypothesis

Exhibit 11-3 The contents of a sample of 26 cans of apple juice showed a standard deviation of 0.06 ounces.We are interested in testing to determine whether the variance of the population is significantly more than 0.003. -Refer to Exhibit 11-3.At 95% confidence,the null hypothesis

A machine produces pipes used in airplanes.The average length of the pipe is 16 inches.The acceptable variance for the length is .3 inches.A sample of 25 pipes was taken.The average length in the sample was 15.95 inches with a variance of .4 inches. a.Construct a 95% confidence interval for the population variance. b.State the null and alternative hypotheses to be tested. c.Compute the test statistic. d.The null hypothesis is to be tested at the 5% level of significance.State the decision rule for the test using the critical value approach. e.What do you conclude about the population variance?

Exhibit 11-8 -Refer to Exhibit 11-8.If the test is to be performed at 95% confidence,the critical value(s)from the table is(are)

Student advisors are interested in determining if the variances of the grades of day students and night students are the same.The following samples are drawn: Test the equality of the variances of the populations at 95% confidence.

We are interested in determining whether or not the variances of the sales at two small grocery stores are equal.A sample of 16 days of sales at each store indicated the following. Are the variances of the populations (from which these samples came)equal? Use $\alpha$ = 0.05.

The value of F_0.01 with 9 numerator and 20 denominator degrees of freedom is