## A college professor is concerned that the two sections of chemistry that he teaches are not performing at the same level

A college professor is concerned that the two sections of chemistry that he teaches are not performing at the same level. To test his claim, he looks at the mean exam score for a random sample of students from each of his classes. In Class 1, the mean exam score for 18 students is 80.8 with a standard deviation of 3.8. In Class 2, the mean exam score for 23 students is 76.5 with a standard deviation of 8.8
. Assume that the population distributions are approximately normal and the population variances are equal.

Find the P
-value for the hypothesis test. Round your answer to four decimal places.
b. Is there sufficient evidence to conclude that the two sections he teaches are not performing at the same level? Test the claim at the 0.10 level of significance.

## Major television networks conducted a joint poll of viewers and asked them if they felt that beer and other

Major television networks conducted a joint poll of viewers and asked them if they felt that beer and other alcoholic beverage commercials targeted teenagers and young adults (those under 21 years old). The results of the survey are as follows.

Age Group Number Surveyed Number of "Yes" Responses
30 or Younger 1000 471
Older than 30 1000 515

Calculate a 90% confidence interval for the difference in the proportions of those older than 30 and those 30 or younger that believe alcoholic beverage commercials targeted teenagers and young adults. Let the 30 or younger age group be Population 1 and let the older than 30 age group be Population 2. Write your answer using interval notation and round the interval endpoints to three decimal places.

## University officials hope that changes they have made have improved the retention rate. Last year, a sample of 1937 freshmen showed that 1537 returned

University officials hope that changes they have made have improved the retention rate. Last year, a sample of 1937 freshmen showed that 1537 returned as sophomores. This year, 1575 of 1915 freshmen sampled returned as sophomores. Determine if there is sufficient evidence at the 0.05
level to say that the retention rate has improved. Let last year's freshmen be Population 1 and let this year's freshmen be Population 2.

a. State the null and alternative hypotheses for the test. Fill in the blank below.
b. Compute the value of the test statistic. Round your answer to two decimal places.
c. Make the decision and state the conclusion in terms of the original question.

## Construct a confidence interval for the ratio of the two population variances using the given information

Construct a confidence interval for the ratio of the two population variances using the given information. Assume the samples come from populations that are approximately normally distributed. Write your answer using interval notation, and round the interval endpoints to four decimal places.

n1=10 , n2=11, s21=7.324, s22=3.601, 95% level of confidence

## A technician compares repair costs for two types of microwave ovens

A technician compares repair costs for two types of microwave ovens (type I and type II). He believes that the repair cost for type I ovens is greater than the repair cost for type II ovens. A sample of 69 type I ovens has a mean repair cost of \$71.66. The population standard deviation for the repair of type I ovens is known to be \$24.27. A sample of 69 type II ovens has a mean repair cost of \$68.79. The population standard deviation for the repair of type II ovens is known to be \$13.63. Conduct a hypothesis test of the technician's claim at the 0.1 level of significance. Let μ1 be the true mean repair cost for type I ovens and μ2 be the true mean repair cost for type II ovens.

a. State the null and alternative hypotheses for the test.
b. Compute the value of the test statistic. Round your answer to two decimal places.
c. Determine the decision rule for rejecting the null hypothesis H0. Round the numerical portion of your answer to two decimal places.
d. Make the decision for the hypothesis test.