# [Get Answer] Calculate the expected counts, under the null hypothesis that the population proportions of women who would develop breast cancer are the same with both treatments.

The Study of Tamoxifen and Raloxifene (STAR) enrolled more than 1900 postmenopausal
women who were at increased risk for breast cancer. Women were randomly assigned to receive
one of the drugs (tamoxifen or raloxifene) daily for five years. During the course of the study,
researchers kept track of which women developed invasive breast cancer and which women did
not. The initial results released in April 2006 revealed that 163 of 9726women in the tamoxifen
group had developed invasive breast cancer, compared to 167of the 9745 women in the
raloxifene group.
a. Organize this information into a 2X2 table.
Tamoxifen

Raloxifene

Total

Breast Cancer
No Breast Cancer
Total
b. Calculate the expected counts, under the null hypothesis that the population proportions of
women who would develop breast cancer are the same with both treatments.
Tamoxifen

Raloxifene

Breast Cancer
No Breast Cancer
c. Conduct a chi-square test on these data. Report the hypotheses, test statistic, and p-value.
Round the test statistic to three decimal places. Use the chi-square distribution table to find a
range for the p-value. If there is no lower limit on the p-value, enter 0 for the lower limit. If there
is no upper limit on the p-value, enter 1for the upper limit.

.

d. Suppose someone else decided to perform a two-sample z-test and found that z and p-value
0.838 Comment on how this compares to the test statistic and p-value you just calculated.
The test statistic of the chi-square test is roughly
the test statistic of the two-sample z-test.