Discussion:
Q: Exam scores of 40 students in a statistics class are shown. (a) Estimate the mean and standard deviation from the sample. (b) Assuming that the data are from a normal distribution, define bins by using method 3 (equal expected frequencies). Use 8 bins. (c) Set up an Excel worksheet for your chi-square calculations, with a column showing the expected frequency for each bin (they must add to 40). (d) Tabulate the observed frequency for each bin and record it in the next column. (e) Carry out the chi-square test, using α= .05. Can you reject the hypothesis that the exam scores came from a normal population? (f) Enter the data into the Visual Statistics data editor in Module 13
(Goodness-of-Fit Tests) and do chi-square tests with varying options. Was Visual Statistics helpful? ExamScores
79 75 77 57 81 70 83 66
81 89 59 83 75 60 96 86
78 76 71 78 78 70 54 60
71 81 79 88 77 82 75 68
77 69 83 79 79 76 78 71