Exam 10: Inference About Means and Proportions With 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 standard error of is

Independent simple random samples are taken to test the difference between the means of two populations whose standard deviations are not known. The sample sizes are n₁ = 25 and n₂ = 35. The correct distribution to use is the

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 95% confidence interval for the difference between the two population means 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

The sampling distribution of is approximated by a

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

Among a sample of 50 M.D.'s (medical doctors) in the city of Memphis, Tennessee, 10 indicated they make house calls; while among a sample of 100 M.D.'s in Atlanta, Georgia, 18 said they make house calls. Determine a 95% interval estimate for the difference between the proportion of doctors who make house calls in the two cities.

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

The following information regarding the ages of full-time and part-time students are given. Using the following data, develop an interval estimate for the difference between the mean ages of the two populations. Use a 5% level of significance.

In order to determine whether or not a driver's education course improves the scores on a driving exam, a sample of 6 students were given the exam before and after taking the course. The results are shown below.Let d = Score After - Score Before. a.Compute the test statistic. b.At 95% confidence using the p-value approach, test to see if taking the course actually increased scores on the driving exam.

Independent random samples of managers' yearly salaries (in $1000) taken from governmental and private organizations provided the following information. At 95% confidence, test to determine if there is a significant difference between the average salaries of the managers in the two sectors.

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

Exhibit 10-1 Salary information regarding male and female employees of a large company is shown below. -Refer to Exhibit 10-1. If you are interested in testing whether or not the average salary of males is significantly greater than that of females, the test statistic is

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 null hypothesis

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.

Babies weighing less than 5.5 pounds at birth are considered "low-birth-weight babies." In the United States, 7.6% of newborns are low-birth-weight babies. The following information was accumulated from samples of new births taken from two counties. a.Develop a 95% confidence interval estimate for the difference between the proportions of low-birth-weight babies in the two counties. b.Is there conclusive evidence that one of the proportions is significantly more than the other? If yes, which county? Explain, using the results of part (a). Do not perform any test.

When each data value in one sample is matched with a corresponding data value in another sample, the samples are known as

The following information was obtained from matched samples regarding the productivity of four individuals using two different methods of production. Let d = Method 1 - Method 2. Is there a significant difference between the productivity of the two methods? Let $\alpha$ = 0.05.

If two independent large samples are taken from two populations, the sampling distribution of the difference between the two sample means

The Dean of Students at UTC has said that the average grade of UTC students is higher than that of the students at GSU. Random samples of grades from the two schools are selected, and the results are shown below. a.Give the hypotheses. b.Compute the test statistic. c.At a 0.1 level of significance, test the Dean of Students' statement.