24. A State of Washington’s Public Interest Research Group (PIRG) study showed that 46%

of full-time college students work 25 or more hours per week. The PIRG study provided data on the effects of working on grades (USA Today,April 17, 2002). A sample of 200 students included 90 who worked 1–15 hours per week, 60 who worked 16–24 hours per week, and 50 who worked 25–34 hours per week. The sample number of students indicating their work had a positive effect, no effect, or a negative effect on grades is as follows.

a. Conduct a test of independence to determine whether the effect on grades is independent of the hours worked per week. Use α  .05. What is the p-value, and what is your conclusion?

b. Use row percentages to learn more about how working affects grades. What is your conclusion?