5.3.9

Researchers Vogel et al. (JAMA, 2006) reported the following findings about the Study of Tamoxifen and Raloxifene (STAR), a study involving postmenopausal women who were at an increased risk for invasive breast cancer. Of the 9,726 women randomly assigned to use tamoxifen daily, 163 developed invasive breast cancer sometime during the next five years, compared to 168 in the group of 9,745 who were randomly assigned to use raloxifene daily.

Explain why it would be okay to use the theory-based method (that is, normal distribution based method) to find a confidence interval for this study.

We can use a theory-based approach because we have a sample size of less than 20.

We can use a theory-based approach because we have at least 10 successes and 10 failures.

We can use a theory-based approach because we have less than 10 successes and 10 failures.

We can use a theory-based approach because we have a sample size of at least 20.

eTextbook and Media

Use anappropriate appletto find and report the theory-based 99% confidence interval.Roundyour answersto 4 decimal places, e.g. 0.0083.

(

Enter your answer; confidence interval, lower bound

,

Enter your answer; confidence interval, upper bound

)

eTextbook and Media

Interpret the 99% confidence interval in the context of the study.

We are 99% confident that the probability of developing invasive breast cancer with tamoxifen is up to 0.0043 higher or up to 0.0053 lower than with raloxifene.

We are 99% confident that the probability of not developing invasive breast cancer with tamoxifen is up to 0.0043 higher or up to 0.0053 lower than with raloxifene.

We are 99% confident that the probability of developing invasive breast cancer with raloxifene is 0.0043 to 0.0053 lower than with tamoxifen.

We are 99% confident that the probability of developing invasive breast cancer with raloxifene is 0.0043 to 0.0053 higher than with tamoxifen.

eTextbook and Media

Relatively speaking, is the 99% confidence interval narrow or wide? Explain why that makes sense.