Question

A car manufacturer claims that its cars make on average 30 miles per gallon on a highway. A consumer group tests 25 cars on a highway and finds the average of 27 miles per gallon and a standard deviation of 5.81 miles per gallon. Do these results doubt the claim made by the car manufacturer about the population mean μ? Test the hypotheses H0: μ =30 versus Ha:μ ≠ 30 at 0.05 level of significance.

Suppose that a test of H0: μ =30 versus Ha: μ ≠ 30 at 0.05 level of significance resulted in rejection of the null hypothesis (“reject of H0” may or may not be the correct answer to the previous question). Evaluate the following statement: If a 95% confidence interval for the population mean mu was constructed, it would have contained 30.

A. true

B. unknown

C. false

D. uncertain

E. none of the others

Answer 1

Sample size. =n= 25