Exam 11: Inferences About Population Variances

The chi-square value for a one-tailed test (lower tail)when the level of significance is 0.1 and the sample size is 15 is

For an F distribution,the number of degrees of freedom for the numerator

A sample of 22 bottles of soft drink showed a variance of 0.64 in their contents.At 95% confidence,determine whether or not the standard deviation of the population is significantly different from 0.7.Use the critical value approach.

Exhibit 11-8 -Refer to Exhibit 11-8.The null hypothesis

You are given the following results from a sample of 6 observations. a.Determine the mean and the variance of this sample. b.Construct a 95% confidence interval for the population standard deviation.

The value of F_.05 with 8 numerator and 19 denominator degrees of freedom is

A sample of 51 elements is selected to estimate a 95% confidence interval for the variance of the population.The chi-square values to be used for this interval estimation 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 test statistic is

The sampling distribution used when making inferences about a single population's variance is

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 test statistic is

The producer of a certain bottling equipment claims that the variance of all their filled bottles is 0.027 or less.A sample of 30 bottles showed a standard deviation of 0.2.The p-value for the test is

The 95% confidence interval estimate for a population variance when a sample variance of 324 is obtained from a sample of 81 items is

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.The test statistic is

To avoid the problem of not having access to tables of the F distribution with values given for the lower tail when a two-tailed test is required,let the smaller sample variance be

A random sample of 21 checking accounts at a bank showed an average daily balance of $430 with a standard deviation of $50. a.Provide a 95% confidence interval estimate of the variance of the population of the checking accounts. b.Provide a 95% confidence interval estimate of the standard deviation of the population of the checking accounts.

A company claims that the standard deviation in their delivery time is less than 5 days.A sample of 27 past customers is taken.The average delivery time in the sample was 14 days with a standard deviation of 4.5 days.At 95% confidence,test the company's claim.Use the critical value approach.

We are interested in testing whether the variance of a population is significantly more than 625.The null hypothesis for this test is

Exhibit 11-8 -Refer to Exhibit 11-8.The test statistic has a value of

A sample of 16 students showed that the variance in the number of hours they spend studying is 25.At 95% confidence,test to see if the variance of the population is significantly different from 30.Use the critical value approach.

ACT scores of a sample of UTC students are shown below. a.Compute the mean and the variance. b.At 95% confidence,test to determine whether or not the variance of the ACT scores of the population of UTC students is significantly more than 8.