a medical researcher wishes to determine the percentage offemales who take vitam

Question

a medical researcher wishes to determine the percentage offemales who take vitamin.he wishes to be 99% confident that theestimate is within 1 percentage points of the true proportion. arecent study of 180 females showed that 25% took vitamins. (a) how large should the sample size be? (b)if no estimate of the sample proportion is available, howlarge should the sample be? (a) how large should the sample size be? (b)if no estimate of the sample proportion is available, howlarge should the sample be?

Explanation / Answer

(a) Given p=0.25, n=180, E=0.01 =0.01, Z(0.005)=2.58 (check normal table) n=(Z/E)^2*p*(1-p)=(2.58/0.01)^2*0.25*(1-0.25) = 12480.75 Take n=12481 ------------------------------------------------------------------------------------ (b) n=(2.58/0.01)^2*0.5*(1-0.5) = 16641

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