Exam 10: Inference About Means and Proportions With Two Populations

The following information regarding the number of semester hours taken from random samples of day and evening students is provided. Develop a 95% confidence interval estimate for the difference between the mean semester hours taken by the two groups of students.

In order to estimate the difference between the average daily sales of two branches of a department store, the following data has been gathered. a.Determine the point estimate of the difference between the means. b.Determine the degrees of freedom for this interval estimation. c.Compute the margin of error. d.Develop a 95% confidence interval for the difference between the two population means.

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 95% confidence interval for the difference between the two proportions 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 p-value is

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?

A potential investor conducted a 144 day survey in each theater in order to determine the difference between the average daily attendance at the North Mall and South Mall theaters. The North Mall Theater averaged 630 patrons per day; while the South Mall Theater averaged 598 patrons per day. From past information, it is known that the variance for North Mall is 1,000; while the variance for the South Mall is 1,304. Develop a 95% confidence interval for the difference between the average daily attendance at the two theaters.

A random sample of 89 tourists in Chattanooga showed that they spent an average of $2,860 (in a week) with a standard deviation of $126; and a sample of 64 tourists in Orlando showed that they spent an average of $2,935 (in a week) with a standard deviation of $138. We are interested in determining if there is any significant difference between the average expenditures of those who visited the two cities? a.Determine the degrees of freedom for this test. b.Compute the test statistic. c.Compute the p-value. d.What is your conclusion? Let $\alpha$ = .05.

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

The management of Regional Hospital has made substantial improvements in their hospital and would like to test and determine whether there has been a significant decrease in the average length of stay of their patients in their hospital. The following data has been accumulated from before and after the improvements. At 95% confidence, test to determine if there has been a significant reduction in the average length of stay. 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 10-3 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 standard error of is

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

The following shows the monthly sales in units of six salespersons before and after a bonus plan was introduced. At 95% confidence, determine whether the bonus plan has increased sales significantly. (For the following matched samples, let the difference "d" be: d = after - before.)

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

A company attempts to evaluate the potential for a new bonus plan by selecting a sample of 4 salespersons to use the bonus plan for a trial period. The weekly sales volume before and after implementing the bonus plan is shown below. (For the following matched samples, let the difference "d" be d = after - before.) a.State the hypotheses. b.Compute the test statistic. c.Use Alpha = .05 and test to see if the bonus plan will result in an increase in the mean weekly sales.

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

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. What is the conclusion that can be reached about the difference in the average final examination scores between the two classes? (Use a .05 level of significance.)

The standard error of is 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. A point estimate for the difference between the two sample means 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 p-value is

Test scores on a standardized test from samples of students from two universities are given below. Provide a 98% confidence interval estimate for the difference between the test scores of the two universities.