To see whether students who nish an exam rst get the same grades as those who nish later, a professor kept track of the order in which papers were handed in. Of the rst 25 papers, 10 received a "B" or better, compared with 8 of the last 24 papers handed in. Research ques- tion: At α = .10, is the grade independent of the order handed in? Since it is a 2 × 2 table, try also a two-tailed, two-sample z test for π1 = π2 (see Chapter 10) and verify that z2 is the same Grades as your chi-square statistic. Which test do you prefer? Why?

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Grade "B or better "C or worse Col Total Earlier Hand-In 10 15 25 Later Hand-in 8 16 24 Row Total 18 31 49