Exam 11: Inferences About Population Variances

A sample of 22 bottles of soft drink showed a variance of 0.64 in their contents. At a 5% level of significance, determine whether or not the standard deviation of the population is significantly different from 0.7.

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Question 1

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Do not reject H_0,there is not sufficient evidence to conclude that the standard deviation of the population is significantly different from 0.7

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

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Question 2

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A professor believes the variability in time to complete tests has increased. In the past, the variance in minutes to complete a particular test was 25. The time it takes to complete a test was recorded for a sample of 15 students. The results follow. Use Excel to determine if the variance in times has increased. Use a .02 level of significance.

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Question 3

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Reject H₀, there is sufficient evidence to conclude that the variance in times has increased

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.

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Question 4

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. e.What do you conclude about the population variance?

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Question 5

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

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Question 6

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? H₀: $A sample of 30 items provided a sample mean of 28 and a sample standard deviation of 6. Test the following hypotheses using \alpha = 0.05. What is your conclusion? H0: 2 < 25 Ha: 2 > 25$ ² < 25 H_a: $A sample of 30 items provided a sample mean of 28 and a sample standard deviation of 6. Test the following hypotheses using \alpha = 0.05. What is your conclusion? H0: 2 < 25 Ha: 2 > 25$ ² > 25

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Question 7

In practice, the most frequently encountered hypothesis test about a population variance is a

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Question 8

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6. The null hypothesis

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Question 9

Exhibit 11-10 -Refer to Exhibit 11-10. The test statistic for this problem equals

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Question 10

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6. The null hypothesis is to be tested at the 10% level of significance. The critical value from the table is

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Question 11

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

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Question 12

The chi-square values (for interval estimation) for a sample size of 10 at 95% confidence are

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Question 13

The specifications for the filling of soft drink bottles is a variance of 0.05 (ounces)². A sample of 20 bottles of soft drink showed the following results. At a 5% level of significance, use Excel to determine whether or not the variance of the population is significantly different from 0.05.

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Question 14

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 25 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

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Question 15

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

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Question 16

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.

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Question 17

The time it takes to complete a test was recorded for a sample of 15 students. The results follow. Use Excel to estimate the variance with a 90% level of confidence.

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Question 18

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

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Question 19

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.

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Question 20

Showing 1 - 20 of 113

A sample of 22 bottles of soft drink showed a variance of 0.64 in their contents. At a 5% level of significance, determine whether or not the standard deviation of the population is significantly different from 0.7.

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

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.

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

In practice, the most frequently encountered hypothesis test about a population variance is a

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6. The null hypothesis

Exhibit 11-10 -Refer to Exhibit 11-10. 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. The null hypothesis is to be tested at the 10% level of significance. The critical value from the table is

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

The chi-square values (for interval estimation) for a sample size of 10 at 95% confidence are

The specifications for the filling of soft drink bottles is a variance of 0.05 (ounces)². A sample of 20 bottles of soft drink showed the following results. At a 5% level of significance, use Excel to determine whether or not the variance of the population is significantly different from 0.05.

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

The time it takes to complete a test was recorded for a sample of 15 students. The results follow. Use Excel to estimate the variance with a 90% level of confidence.

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

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.

Data and Statistics

Descriptive Statistics: Tabular and Graphical Displays

Descriptive Statistics: Numerical Measures

Introduction to Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Interval Estimation

Hypothesis Tests

Inference About Means and Proportions With Two Populations

Tests of Goodness of Fit, Independence and Multiple Proportions

Experimental Design and Analysis of Variance

Simple Linear Regression

Multiple Regression

Regression Analysis: Model Building

Time Series Analysis and Forecasting

Nonparametric Methods

Statistical Methods for Quality Control

Decision Analysis

Sample Survey

Filters

Exam 11: Inferences About Population Variances

A sample of 22 bottles of soft drink showed a variance of 0.64 in their contents. At a 5% level of significance, determine whether or not the standard deviation of the population is significantly different from 0.7.

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

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.

Do the following data indicate that the variance of the population from which this sample has been drawn is 17? Use α\alphaα = 0.05.

A sample of 30 items provided a sample mean of 28 and a sample standard deviation of 6. Test the following hypotheses using α\alphaα = 0.05. What is your conclusion? H0: 2 < 25 Ha: 2 > 25

In practice, the most frequently encountered hypothesis test about a population variance is a

Exhibit 11-6 We want to test the hypothesis that the population variances are equal. -Refer to Exhibit 11-6. The null hypothesis

Exhibit 11-10 -Refer to Exhibit 11-10. 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. The null hypothesis is to be tested at the 10% level of significance. The critical value from the table is

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

The chi-square values (for interval estimation) for a sample size of 10 at 95% confidence are

The specifications for the filling of soft drink bottles is a variance of 0.05 (ounces)2. A sample of 20 bottles of soft drink showed the following results. At a 5% level of significance, use Excel to determine whether or not the variance of the population is significantly different from 0.05.

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

The time it takes to complete a test was recorded for a sample of 15 students. The results follow. Use Excel to estimate the variance with a 90% level of confidence.

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

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.

Data and Statistics

Descriptive Statistics: Tabular and Graphical Displays

Descriptive Statistics: Numerical Measures

Introduction to Probability

Discrete Probability Distributions

Continuous Probability Distributions

Sampling and Sampling Distributions

Interval Estimation

Hypothesis Tests

Inference About Means and Proportions With Two Populations

Tests of Goodness of Fit, Independence and Multiple Proportions

Experimental Design and Analysis of Variance

Simple Linear Regression

Multiple Regression

Regression Analysis: Model Building

Time Series Analysis and Forecasting

Nonparametric Methods

Statistical Methods for Quality Control

Decision Analysis

Sample Survey

Filters

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

The specifications for the filling of soft drink bottles is a variance of 0.05 (ounces)². A sample of 20 bottles of soft drink showed the following results. At a 5% level of significance, use Excel to determine whether or not the variance of the population is significantly different from 0.05.