Exam 10: Statistical Inference About Means and Proportions With Two Populations

Exhibit 10-11 An insurance company selected samples of clients under 18 years of age and over 18 and recorded the number of accidents they had in the previous year.The results are shown below. We are interested in determining if the accident proportions differ between the two age groups. -Refer to Exhibit 10-11 and let p_u represent the proportion under and po the proportion over the age of 18.The null hypothesis is

To compute an interval estimate for the difference between the means of two populations,the t distribution

Maxforce,Inc. ,manufactures racquetball racquets by two different manufacturing processes (A and B).Because the management of this company is interested in estimating the difference between the average time it takes each process to produce a racquet,they select independent samples from each process.The results of the samples are shown below. a.Develop a 95% confidence interval estimate for the difference between the average time of the two processes. b.Is there conclusive evidence to prove that one process takes longer than the other? If yes,which process? Explain.

Two independent samples are drawn from two populations,and the following information is provided. We want to test the following hypotheses. a.Determine the degrees of freedom. b.Compute the test statistic. c.At 95% confidence,test the hypotheses.Assume the two populations are normally distributed and have equal variances.

Zip,Inc.manufactures Zip drives on two different manufacturing processes.Because the management of this company is interested in determining if process 1 takes less manufacturing time,they selected independent samples from each process.The results of the samples are shown below. a.State the null and alternative hypotheses. b.Determine the degrees of freedom for the t test. c.Compute the test statistic d.At 95% confidence,test to determine if there is sufficient evidence to indicate that process 1 takes a significantly shorter time to manufacture the Zip drives.

Exhibit 10-12 The results of a recent poll on the preference of teenagers regarding the types of music they listen to are shown below. -Refer to Exhibit 10-12.The point estimate for the difference between the proportions is

Exhibit 10-2 The following information was obtained from matched samples. The daily production rates for a sample of workers before and after a training program are shown below. -Refer to Exhibit 10-2.The point estimate for the difference between the means of the two populations is

Independent random samples taken on two university campuses revealed the following information concerning the average amount of money spent on textbooks during the fall semester. We want to determine if,on the average,students at University A spent more on textbooks then the students at University B. a.Compute the test statistic. b.Compute the p-value. c.What is your conclusion? Let $\alpha$ = .05.

In order to estimate the difference between the average Miles per Gallon of two different models of automobiles,samples are taken and the following information is collected. a.At 95% confidence develop an interval estimate for the difference between the average Miles per Gallon for the two models. b.Is there conclusive evidence to indicate that one model gets a higher MPG than the other? Why or why not? Explain.

Exhibit 10-10 The results of a recent poll on the preference of shoppers regarding two products are shown below. -Refer to Exhibit 10-10.The 95% confidence interval estimate for the difference between the populations favoring the products is

Exhibit 10-7 In order to estimate the difference between the average hourly wages of employees of two branches of a department store,the following data have been gathered. -Refer to Exhibit 10-7.A point estimate for the difference between the two sample means is

Exhibit 10-12 The results of a recent poll on the preference of teenagers regarding the types of music they listen to are shown below. -Refer to Exhibit 10-12.The standard error of Is

Exhibit 10-13 In order to determine whether or not there is a significant difference between the hourly wages of two companies,the following data have been accumulated. -Refer to Exhibit 10-13.The null hypothesis for this test is

Exhibit 10-1 Salary information regarding male and female employees of a large company is shown below. -Refer to Exhibit 10-1.The p-value is

Exhibit 10-7 In order to estimate the difference between the average hourly wages of employees of two branches of a department store,the following data have been gathered. -Refer to Exhibit 10-7.A 95% interval estimate for the difference between the two population means is

Exhibit 10-11 An insurance company selected samples of clients under 18 years of age and over 18 and recorded the number of accidents they had in the previous year.The results are shown below. We are interested in determining if the accident proportions differ between the two age groups. -Refer to Exhibit 10-11.The test statistic is

In a random sample of 200 Republicans,160 opposed the new tax laws.While in a sample of 120 Democrats,84 opposed the new tax laws.Determine a 95% confidence interval estimate for the difference between the proportions of Republicans and Democrats opposed to this new law.

The daily production rates for a sample of factory workers before and after a training program are shown below.Let d = After - Before. We want to determine if the training program was effective. a.Give the hypotheses for this problem. b.Compute the test statistic. c.At 95% confidence,test the hypotheses.That is,did the training program actually increase the production rates?

Exhibit 10-3 A statistics teacher wants to see if there is any difference in the abilities of students enrolled in statistics today and those enrolled five years ago.A sample of final examination scores from students enrolled today and from students enrolled five years ago was taken.You are given the following information. -Refer to Exhibit 10-3.The test statistic for the difference between the two population means is

In a sample of 100 Republicans,60 favored the President's anti-drug program.While in a sample of 150 Democrats,84 favored his program.At 95% confidence,test to see if there is a significant difference in the proportions of the Democrats and the Republicans who favored the President's anti-drug program.