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Exam 11: Inferences About Population Variances

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Question 1

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Exhibit 11-5 -Refer to Exhibit 11-5.The test statistic for this problem equals

A) .63
B) 12.68
C) 13.33
D) 13.66

E) None of the above
F) A) and D)

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Question 2

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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?

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a.H₀: ²1

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Question 3

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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.At 95% confidence the null hypothesis

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6.The test statistic for this problem equals

The average grade of a sample of 30 students on their second statistics examination was 85 with a standard deviation of 11.Is the variance of the population significantly more than 80? Use a 0.05 level of significance.

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 test statistic for this problem equals

Which of the following has a chi-square distribution?

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 11-4 -Refer to Exhibit 11-4.The p-value is between

A sample of n observations is taken from a population.The appropriate chi-square distribution has

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

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.

The symbol used for the variance of the sample is

A sample of 20 cans of tomato juice showed a standard deviation of 0.4 ounces.A 95% confidence interval estimate of the variance for the population is

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

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.

A sample of 61 observations yielded a sample standard deviation of 6.If we want to test H_o: $\sigma$ ² = 40,the test statistic is

The 90% confidence interval estimate for a population standard deviation when a sample variance of 50 is obtained from a sample of 15 items is

At $\alpha$ = 0.1,test to see if the population variances from which the following samples were drawn are equal.

A random sample of 20 observations showed a standard deviation of 8.At 95% confidence,test to see if the variance of the population is significantly less than 65.Use the critical value approach.