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Exam 11: Inferences About Population Variances

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Question 31

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A large company has claimed that the standard deviation of the monthly incomes of their employees is less than or equal to $120. To test their claim, a random sample of 76 employees of the company was taken; and it was determined that the standard deviation of their incomes was $135. At 90% confidence, test the company's claim.

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H₀: ² 14400
H_a: ²> 14400...

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Question 32

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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?

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² = 90.75 > 79.082; r...

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Question 33

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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 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 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)

The 99% confidence interval estimate for a population variance when a sample standard deviation of 12 is obtained from a sample of 10 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 null hypothesis is

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

An egg packing company has stated that the standard deviation of the weights of their grade A large eggs is 0.07 ounces or less. The sample variance for 51 eggs was 0.0065 ounces. Can this sample result confirm the company's claim? Use $\alpha$ = 0.1.

It has been suggested that night shift-workers show more variability in their output levels than day workers. Below, you are given the results of two independent random samples. 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?

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6. The p-value is between

A sample of 30 items provided a sample mean of 28 and a sample standard deviation of 6. Test the following hypotheses using $\alpha$ = 0.05. What is your conclusion?

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.

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 p-value for this test 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

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

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?

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)

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

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