Exam 8: Estimation: Additional Topics

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A restaurant manager was in charge of purchasing new microwaves for his restaurant.The choices were narrowed to two available models.Since the two models cost about the same,the manager was interested in determining whether there was a difference in the amount of power consumed when operated at high voltages.Based on two independent random samples,the following summary information was computed: -Find a 95% confidence interval for the difference in the amount of power consumed at high voltages by the two models.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The means and variances are obtained from two independent samples.Assume that the populations from which the samples were drawn have unequal variances. -Determine the number of degrees of freedom for n₁ = 9, = 24,n₂ = 14,and = 36

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A dependent random sample from two normally distributed populations gives the following results: n = 20; = 14.8;s_d = 4.0 -Find the margin of error for a 99% confidence interval for the difference between the means of the two populations.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: n₁ = 35, ₁ = 140 = 60.84;n₂ = 48, ₂ = 130,and = 156.25 -What is the lower confidence limit of the 95% confidence interval?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A confidence interval for the difference between the means of two normally distributed populations based on the following dependent samples is desired: -What is the upper confidence limit of the 95% confidence interval?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The means and variances are obtained from two independent samples.Assume that the populations from which the samples were drawn have unequal variances. -Determine the number of degrees of freedom for n₁ = 5, = 32,n₂ = 10,and = 40.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A dependent random sample from two normally distributed populations gives the following results: n = 20; = 14.8;s_d = 4.0 -Find the width of the 99% confidence interval.

The formula used to determine the number of degrees of freedom for the t distribution is (n₁ + n₂ - 2).

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: For calculating a 95% confidence interval for μ₁ - μ₂ the difference between the means of two normally distributed populations,the summary statistics from two independent samples are: n_x = 60, = 180, = 360,n_y = 45, = 160,and = 900. It is assumed that the Population variances are unknown and are equal. -What is the upper confidence limit of the 95% confidence interval?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A dependent random sample from two normally distributed populations gives the following results: n = 20, = 26.5,s₂ = 3.2 -What is the lower confidence limit of the 98% confidence interval for the difference between the population means?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A career counselor is interested in examining the salaries earned by graduate business school students at the end of the first year after graduation.In particular,the counselor is interested in seeing whether there is a difference between men and women graduates' salaries.From a random sample of 20 men,the mean salary is found to be $42,780 with a standard deviation of $5,426.From a sample of 12 women,the mean salary is found to be $40,136 with a standard deviation of $4,383.Assume that the random sample observations are from normally distributed populations,and that the population variances are assumed to be equal. -What is the upper confidence limit of the 95% confidence interval for the difference between the population mean salary for men and women?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A computer information systems manager was in charge of purchasing new battery packs for laptop computers.The choices were narrowed to two available models.Since the two models cost about the same,the manager was interested in determining whether there was a difference in the average time the battery packs would function before needing to be recharged.Based on two independent random samples,the following summary information was computed: -Find a 95% confidence interval for the difference in average functioning time before recharging the two models.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A computer information systems manager was in charge of purchasing new battery packs for laptop computers.The choices were narrowed to two available models.Since the two models cost about the same,the manager was interested in determining whether there was a difference in the average time the battery packs would function before needing to be recharged.Based on two independent random samples,the following summary information was computed: -Based on the 95% confidence interval,can one conclude that there is a difference in the true average functioning time between the two models of battery packs before recharging? Justify your answer.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A dependent random sample from two normally distributed populations gives the following results: n = 20, = 26.5,s₂ = 3.2 -What is the upper confidence limit of the 98% confidence interval for the difference between the population means?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: = 19.56 s_d = 2.5 and n = 20 -Calculate the width of the interval for a 95% confidence interval.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: In a random sample of 150 large retailers,110 used regression as a method of forecasting.In an independent random sample of 180 small retailers,90 used regression as a method of forecasting. -Find the 90% confidence interval for the difference between the two population proportions.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The residents of Austin,Texas,complain that parking fines given in their city are higher than the parking fines that are given in Houston.Independent random samples of the amounts paid by residents for parking tickets in each of two cities over the last four months were obtained.Assume the population variances are equal.These amounts were as follows: -Find the 98% confidence interval for the difference in the mean costs of parking tickets in these two cities.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A dependent random sample from two normally distributed populations gives the following results: n = 20, = 26.5,s₂ = 3.2 -The confidence interval for the difference between two population means that are normally distributed where the population variances are unknown but assumed to be equal rely on:

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A restaurant manager was in charge of purchasing new microwaves for his restaurant.The choices were narrowed to two available models.Since the two models cost about the same,the manager was interested in determining whether there was a difference in the amount of power consumed when operated at high voltages.Based on two independent random samples,the following summary information was computed: -Find a 99% confidence interval for the difference in the amount of power consumed at high voltages by the two models.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The means and variances are obtained from two independent samples.Assume that the populations from which the samples were drawn have unequal variances. -Determine the number of degrees of freedom for n₁ = 10, = 5,n₂ = 12,and = 9.