Question

Literature shows that the incidence of breast cancer is 150 cases per 100,000 women aged 45-49 years old annually. The researchers want to test whether regular intake of vitamin D would reduce 20% of the risk of the occurence of breast cancer. They plan to recruit women aged 45-49 years who are free of breast cancer at the beginning and randomly assign them into two groups, i.e., group one: women in this group will receive vitamin D treatment, and group two: women in this group will receive placebo.

a) if the ratio is 1:1, the significant level is set at 0.05 with 85% of power, how many women aged 45-49 years are needed for this study?

Answer 1

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ANSWER ::-

AS FOR GIVEN DATA...

Literature shows that the incidence of breast cancer is 150 cases per 100,000 women aged 45-49 years old annually. The researchers want to test whether regular intake of vitamin D would reduce 20% of the risk of the occurence of breast cancer. They plan to recruit women aged 45-49 years who are free of breast cancer at the beginning and randomly assign them into two groups, i.e., group one: women in this group will receive vitamin D treatment, and group two: women in this group will receive placebo.

SOL ::-

a) if the ratio is 1:1, the significant level is set at 0.05 with 85% of power, how many women aged 45-49 years are needed for this study?

ANS ::-

would be the 150/100000=0.0015 and

is the probability of event in the control group and is the probability of event in the experimental group. Probability of the event in the experimental group is expected to be less by 20% Hence =0.0012

a)there fore

=82.6~83

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