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# Is there evidence that the mean cost for student textbooks at the University of China is above \$310?

3. The director of admissions at the University of China is concerned about the high cost of textbooks for the students each semester. A sample of 20 students enrolled in the university indicates that X (bar) = \$316.4 and s = \$43.20. Answer the following questions in detail by using Excel.

a. Using the 0.10 level of significance, is there evidence that the population mean is above \$310
b. What is your answer in (a) if s = \$75 and the 0.05 level of significance is used?
c. What is your answer in (a) if X (bar) = \$305.11 and s = \$43.20?
d. Based on the information in part (a), what decision should the director make about the books used for the courses if the goal is to keep the cost below \$300?

#### Solution Preview

3. The director of admissions at the University of China is concerned about the high cost of textbooks for the students each semester. A sample of 20 students enrolled in the university indicates that X (bar) = \$316.4 and s = \$43.20.

a. Using the 0.10 level of significance, is there evidence that the population mean is above \$310?

Null Hypothesis: Mean= \$310

Alternative Hypothesis: Mean> \$310

Mean=M =\$310.00

Standard deviation =s=\$43.20

sample size=n=20

sx=standard error of mean=s/square root of n=9.6598= ( 43.2 /square root of 20)

Significance level=a (alpha) =0.1or10%

No of tails=1

This is a 1tailed test because we are testingM 1>M 2

Since sample size=20<30

and we are estimating the population standard deviation from sample standard deviation

we will use t distribution

sample mean=\$316.40

t at the 0.1 level of significance and 19 degrees of freedom (=n-1) and1 tailed test=1.3277

Upper ...

#### Solution Summary

This solution provides calculations for testing the hypothesis that the population mean is above \$310 in plain text and in an attached Word document.

\$2.19