Math 143 C/E, Spring 2001
IPS Reading Questions
Chapter 8, Section 2



  1. The data in the table at the top of p. 603 can be thought of as having been collected using questionnaires which asked for two pieces of information (i.e., two variables) from each respondent: the gender of the respondent, and the respondent's status as a binge drinker. A different type of table (than the one on p. 603), called a two-way table, can be constructed to summarize the information collected using such a survey. While you have yet to do any reading regarding two-way tables (and I am not asking you to do any now either), try your hand at constructing one following this brief description:
    Along the top, write column headers for each value of one of the two variables, perhaps “gender”. Along the rows, write down row “headings” for each value of the other variable (this would be “drinking status” if you used “gender” for the columns). You should now have headings for two columns and two rows. Add a third column for “Totals” and similarly a third row for “Totals”. Now fill in the 9 entries of the table with the appropriate counts.
    Compare your result to Table 2.14 on p. 194.











  2. Why does it make more sense when performing a test of significance for the difference in two (independent) proportions to use a pooled estimate (defined at the bottom of p. 604) in the calculation of the spread sD than to use one of the proportions 1 or 2 that arise from the samples?















  3. The authors say in several places that the sample sizes n1 and n2 should be large. At the top of p. 606, they remind us why this is necessary: because we are using the normal approximation to distributions that truly are binomial (at least, binomial for the counts X1 and X2). For 1-sample procedures, what was the criterion that had to be met in order to use such a binomial approximation? How has this criterion been modified for 2-sample procedures?













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