Smoking and cervical cancer. Table 19.9 displays data from a case–

control study on smoking and invasive cervical cancer with data stratified by number of sexual partners.

(a) Calculate the odds ratios within each stratum. Comment on your findings.

(b) Test the odds ratios for interaction. Report the chi-square interaction statistic, its df, and P-value.

(c) Merge the data from the two strata, and then calculate the crude odds ratio. How would data have been misinterpreted had it not been stratified by the number of sexual partners?

(d) Rearrange the data to determine whether having two or more partners is a risk factor for invasive cervical cancer. Calculate the odds ratio. Consider these results in light of prior analyses in this exercise.