Wk 6

The null and

Alternate hypotheses are:

A random sample of 20 items from the first population showed a mean of 100 and a standard

deviation of 15. A sample of 16 items for the second population showed a mean of

94 and a standard deviation of 8. Use the .05 significant level.

An investigation of the effectiveness of an antibacterial soap in reducing operating room contamination

resulted in the accompanying table. The new soap was tested in a sample of eight

operating rooms in the greater Seattle area during the last year. The following table reports

the contamination levels before and after the use of the soap for each operating room.

At the .05 significance level, can we conclude the contamination measurements are lower

after use of the new soap?

Refer to the Baseball 2016 data, which report information on the 30 Major League Baseball

teams for the 2016 season.

a. At the .05 significance level, can we conclude that there is a difference in the mean salary

of teams in the American League versus teams in the National League?

b. At the .05 significance level, can we conclude that there is a difference in the mean

home attendance of teams in the American League versus teams in the National

League?

c. Compute the mean and the standard deviation of the number of wins for the 10 teams

with the highest salaries. Do the same for the 10 teams with the lowest salaries. At the

.05 significance level, is there a difference in the mean number of wins for the two

groups?

Refer to the Buena School District bus data. Is there a difference in the mean maintenance

cost for the diesel versus the gasoline buses? Use the .05 significance level.

Refer to the description of Century National Bank at the end

of the Review of Chapters 1–4 on page 128.

With many other options available, customers no longer

let their money sit in a checking account. For many

years the mean checking balance has been $1,600. Do the

sample data indicate that the mean account balance has

declined from this value?

Recent years have also seen an increase in the use of

ATM machines. When Mr. Selig took over the bank, the

mean number of transactions per month per customer was

8; now he believes it has increased to more than 10. In fact,

the advertising agency that prepares TV commercials for

Century would like to use this on the new commercial being

designed. Is there sufficient evidence to conclude that

the mean number of transactions per customer is more than

10 per month? Could the advertising agency say the mean

is more than 9 per month?

The bank has branch offices in four different cities:

Cincinnati, Ohio; Atlanta, Georgia; Louisville, Kentucky; and

Erie, Pennsylvania. Mr. Selig would like to know whether

there is a difference in the mean checking account balances

among the four branches. If there are differences, between

which branches do these differences occur?

Mr. Selig is also interested in the bank’s ATMs. Is there

a difference in ATM use among the branches? Also, do customers

who have debit cards tend to use ATMs differently

from those who do not have debit cards? Is there a difference

in ATM use by those with checking accounts that pay

interest versus those that do not? Prepare a report for

Mr. Selig answering these questions.