Thrombotic stroke in young women. A 1970s case–control study on cerebrovascular disease (stroke) and oral contraceptive use in young women matched cases to controls according to neighborhood, age, sex, and race.bb Table 18.26 displays data from this study for thrombotic stroke.

(a) Calculate the odds ratio for these data. Briefly, interpret the results in narrative form.

(b) Suppose the match was broken and investigators analyzed the data as if derived from independent samples. Rearrange the information in Table 18.26 to show how it would appear in a two-by-two table of unmatched counts. Because the matchedpair table (Table 18.26) includes 106 pairs, your new table should total 212 individuals. Calculate the odds ratio for the data with the match broken. How does this compare to that of the

(proper) matched-pair odds ratio?