Refer to the previous exercise about the study of different HIV intervention programs. Show how to calculate the chi-square statistic by setting up the formula with appropriate numbers.

Data from previous exercise

Researchers Jemmott III et al. (Journal of American Medical Association, 1998) reported a study in which a group of inner-city African American adolescents from Philadelphia were randomly divided into three groups as part of an experiment to assess the effectiveness of different HIV prevention programs. One group was given €œabstinence HIV intervention,€ the next group was given €œsafer-sex HIV intervention,€ and the third group was given €œhealth promotion intervention,€ which was to serve as a control. One outcome that was measured was whether subjects who were sexually active during a three-month period reported consistent condom use. The following table shows the summarized data.

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Safer-sex intervention 20 Abstinence Total Control 21 20 41 intervention 14 Yes 55 Consistent condom use? 52 No 20 12 Total 107 34 32