8. The 1991 General Social Survey asked respondents, "How many sex partners have you had in the last 12 months?" Table 3.13 shows results for 637 respondents.

a) Calculate and interpret the median and the mode.

TABLE 3.12 How Often Had Sex Frequency Not at all 292 Once or twice 99 About once a month 108 2 or 3 times a month 181 About once a week 233 2 or 3 times a week 265 72 More than 3 times a week

b) For the highest 11 valucs, we know only an interval within which the observation fell. To approximate these values, we could use midpoint scores. For instance, for inter al 5- 10. usc (5+10)/2=7.5. We must choose an arbitrary score over 100 for the final interval. Using 120 for that observation, calculate the mean response. Compare to the median, and interpret.

c) Suppose the highest two observations were misrecorded, and the actual values were 4 for each. Recompute the mean and median, and use this example to describe potential effects of outliers on these measures. TABLE 3.13 Number of Sex Partners Frequency 0 146 418 2 39 3 15 4 8 5-10 7 11-20 2 21-100 ' More than 100 I