Chapter 11.2, Problem 66E

Preliminary data analyses and other information indicate that you can reasonably assume that, in Exercises 11.63–11.68, the variable under consideration is normally distributed on both populations. For each exercise, use either the critical-value approach or the P-value approach to perform the required hypothesis test.

11.66 Stuttering. Researchers S. Reilly et al. studied the indicators of stuttering onset and the potential effects that stuttering may have on a child in the article “Natural History of Stuttering to 4 Years of Age: A Prospective Community-Based Study” (Pediatrics, Vol. 132, Issue 3, pp. 460–467). The following table provides the scores on the Communication and Symbolic Behavior Scale (CSBS), an assessment tool used to identify communication disorders, for random samples of stuttering and nonstuttering children.

At the 10% significance level, do the data provide sufficient evidence to conclude that, in this age group, there is more variation in CSBS scores for stutterers than for nonstutterers? (Note: s₁ = 17.326 and s₂ = 15.745.)