Extracurricular activities and grades. In Exercise 24.4, you described the relationship between extracurricular activities and success in a required course. Is the observed association between these variables statistically significant? To find out, proceed as follows.

(a) Add the row and column totals to the two-way table in Exercise 24.4 and find the expected cell counts. Which observed counts differ most from the expected counts?

(b) Find the chi-square statistic. Which cells contribute most to this statistic?

(c) What are the degrees of freedom? Use Table 24.1 to say how significant the chi-square test is. Write a brief conclusion for your study.