Find a 95% confidence interval for the difference in proportions of women who get invasive breast cancer taking HRT vs taking a placebo.

Refer to a study on hormone replacement therapy. Until 2002, hormone replacement therapy (HRT), taking hormones to replace those the body no longer makes after menopause, was commonly prescribed to post-menopausal women. However, in 2002 the results of a large clinical trial were published, causing most doctors to stop prescribing it and most women to stop using it, impacting the health of millions of women around the world. In the experiment, 8506 women were randomized to take HRT and 8102 were randomized to take a placebo. Table 6.8 shows the observed counts for several conditions over the five years of the study.

Table 6.8 

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Condition HRT Group Placebo Group Cardiovascular Disease Invasive Breast Cancer Cancer (all) Fractures 164 122 166 124 502 458 650 788