Refer to the Acoustical Science & Technology (Vol. 35, 2014) study of irrelevant speech effects, Exercise 8.47 (p. 392). Recall that 71 subjects performed a memorization task under two conditions: (1) with irrelevant background speech and (2) in silence. Descriptive statistics on the relative difference in the error rates (RDER) for the two conditions yielded x̅ = 78.2 percent and s = 63.2 percent. Suppose the researchers theorize that the true standard deviation of the RDER values differs from 60 percent.
a. Set up the null and alternative hypotheses for testing the researchers' theory.
b. Compute the test statistic.
c. Find the rejection region of the test using a = .01.
d. Use statistical software to find the p-value of the test.
e. Make the appropriate practical conclusion. State your answer in the words of the problem.
f. What assumption about the population of RDER values must hold true for the inference, part e, to be valid?