Chapter 11, Problem 1FDA

Recall from Chapter 1 (see page 34) that the Focus database and Focus sample contain information on the undergraduate students at the University of Wisconsin - Eau Claire (UWEC). Now would be a good time for you to review the discussion about these data sets.

Open the Focus sample worksheet (FocusSample) in the technology of your choice and then do the following.

1. a. At the 5% significance level, do the data provide sufficient evidence to conclude that the standard deviation of ACT composite scores of all UWEC undergraduates differs from 3 points?
2. b. Determine and interpret a 95% confidence interval for the standard deviation of ACT composite scores of all UWEC undergraduates.
3. c. Obtain a normal probability plot and a box plot of the ACT composite scores of the sampled UWEC undergraduates.
4. d. Based on your results from part (c), do you think that performing the inferences in parts (a) and (b) is reasonable? Explain your answer.
5. e. At the 5% significance level, do the data provide sufficient evidence to conclude that the standard deviations of ACT English scores and ACT math scores differ for UWEC undergraduates?
6. f. Determine and interpret a 95% confidence interval for the ratio of the standard deviation of ACT English scores to the standard deviation of ACT math scores for UWEC undergraduates.
7. g. Obtain normal probability plots and boxplots of the ACT English scores and the ACT math scores of the sampled UWEC undergraduates.
8. h. Based on your results from part (g), do you think that performing the inference in parts (e) and (f) is reasonable? Explain your answer.