The Study of (STAR study) enrolled more than 19, 000 postmenopausal women who we
ID: 3219538 • Letter: T
Question
The Study of (STAR study) enrolled more than 19, 000 postmenopausal women who were at increased risk for breast cancer. Women were randomly assigned to receive one of the drugs daily for five years. Initial results revealed that 163 of the 9726 women in the group had developed invasive breast cancer, compared to 167 of the 9745 women in the group. a) Is this an observational study or an experiment? Circle one. b) Can we do inference based on a normal distribution? For the group, is the count of "successes" greaterthanorequalto 10? Is the count of "failures" greaterthanorequalto 10? Show how you arrived at your answer. For the group, is the count of "successes" greaterthanorequalto 10? Is the count of "failures" greaterthanorequalto 10? Show how you arrived at your answer. random samples? c) Using the applet (not by hand), conduct a 4-step significance test to see if these data give evidence that the drugs there is a difference in the effectiveness of the drugs in lowering the incidence of invasive breast cancer.Explanation / Answer
Q.5 (a) It is an experiment because women are provided one of the drugs so they are not observed, they are experimented.
(b) (i) for the tamoxifen group, the count of success is equal to 163 which is greater than 10 and count of failures are around (9726 - 163=9563) , which is also greater than 10.
(ii) for the raloxifen group, the count of success is equal to 167 which is greater than 10 and count of failures are around (9745 - 167=9578) , which is also greater than 10.
(c) Random sample - Yes samples are completely random as they are randomly selected from postmanopausal women and they are also randomly assigned the drugs.
(c) Step :1
Null HYpothesis : ptamoxifen = praloxifene
ALternative Hypothesis : ptamoxifen = praloxifene
Step : 2 Test Statistic
ptamoxifen = 163/9726 = 0.01676
praloxifene = 167/9745 = 0.017137
p* = (163 + 167)/( 9726 + 9745) = 0.01695
Z = (praloxifene - ptamoxifen )/ sqr [ p*(1- p*) (1/n1 + 1/n2 )]
= ( 0.01737 - 0.01676)/ sqrt [ 0.01695 * 0.98305 * (1/9726 + 1/9745)]
= 0.00061/ 0.001850
= 0.3297
Step : 3 Z critical = 1.96 for 0.05 significance level .
P - value = 0.7416
Step : 4 Here we can not reject the null hypothesis because P - vlaue > 0.05 so we can say that there is no difference between both drugs effectiveness.
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