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.

a. Is this an experiment or an observational study? How are you deciding?
b. Identify the observational units.
c. Identify the explanatory and response variables. Also, for each variable, identify whether it is categorical or quantitative.
d. Define the parameters of interest. Assign symbols to these parameters.
e. State the appropriate null and alternative hypotheses.
f. Find the table of expected cell counts; that is, complete the following table, assuming the null hypothesis is true.

g. Describe how one might use everyday items (for example, coins, dice, cards, etc.) to conduct a tactile simulation-based test of the hypotheses. Be sure to clearly describe how the p-value will be computed from the simulation.

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