Exam 10: Inference About Means and Proportions With Two Populations

Exhibit 10-8 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 10-8. The test statistic is

The reliability of two types of machines used in the same manufacturing process is to be tested. The first machine failed to operate correctly in 90 out of 300 trials while the second type failed to operate correctly in 50 out of 250 trials. a.Give a point estimate for the difference between the population proportions of these machines. b.Calculate the pooled estimate of the population proportion. c.Carry out a hypothesis test to check whether there is a statistically significant difference in the reliability for the two types of machines using a .10 level of significance.

If we are interested in testing whether the proportion of items in population 1 is larger than the proportion of items in population 2, the

The following sample information is given concerning the ACT scores of high school seniors form two local schools. Develop a 95% confidence interval estimate for the difference between the two populations.

Exhibit 10-1 Salary information regarding male and female employees of a large company is shown below. -Refer to Exhibit 10-1. At 95% confidence, the margin of error is

In order to estimate the difference between the average yearly salaries of top managers in private and governmental organizations, the following information was gathered. Develop an interval estimate for the difference between the average salaries of the two sectors. Let $\alpha$ = .05.

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. Based on the results of question 18, the

Exhibit 10-8 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 10-8. The p-value is

The management of Recover Fast Hospital (RFH) claims that the average length of stay in their hospital after a major surgery is less than the average length of stay at General Hospital (GH). The following data have been accumulated to test their claim. a.Formulate the hypotheses. b.Compute the test statistic. c.Using the p-value approach, test to see if the average length of stay in RFH is significantly less than the average length of stay in GH. Let $\alpha$ = 0.05.

Exhibit 10-1 Salary information regarding male and female employees of a large company is shown below. -Refer to Exhibit 10-1. The 95% confidence interval for the difference between the means of the two populations is

Exhibit 10-1 Salary information regarding male and female employees of a large company is shown below. -Refer to Exhibit 10-1. The standard error for the difference between the two means is

Consider the following results for two samples randomly taken from two populations. a.What are the degrees of freedom for the t distribution? b.At 95% confidence, compute the margin of error. c.Develop a 95% confidence interval for the difference between the two population means.

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

Exhibit 10-9 Two major automobile manufacturers have produced compact cars with the same size engines. We are interested in determining whether or not there is a significant difference in the MPG (miles per gallon) of the two brands of automobiles. A random sample of eight cars from each manufacturer is selected, and eight drivers are selected to drive each automobile for a specified distance. The following data show the results of the test. -Refer to Exhibit 10-9. The test statistic is

Exhibit 10-4 The following information was obtained from independent random samples.Assume normally distributed populations with equal variances. -Refer to Exhibit 10-4. The point estimate for the difference between the means of the two populations is

The following are the test scores of two samples of students from University A and University B on a national statistics examination. Develop a 95% confidence interval estimate for the difference between the mean scores of the two populations.

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

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 null hypothesis to be tested is H₀: $\mu$ _d = 0. The test statistic 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.

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.