For this problem, carry at least four digits after the decimal in your calculations. Answers may vary slightly due to rounding.

A random sample of medical files is used to estimate the proportion *p* of all people who have blood type B.

(a) If you have no preliminary estimate for *p*, how many medical files should you include in a random sample in order to be 85% sure that the point estimate p̂ will be within a distance of 0.04 from *p*? (Round your answer up to the nearest whole number.)

medical files

(b) Answer part (a) if you use the preliminary estimate that about 7 out of 90 people have blood type B.

medical files

medical files

(b) Answer part (a) if you use the preliminary estimate that about 7 out of 90 people have blood type B.

medical files

Community Answer

Step 1From the given information,Confidence level =0.80Margin of error =0.04 Step 2Thus,a.Let p be the proportion which is assumed to be 0.50The required sample size can be computed as:ME=Zα/2×p×1-pn0.04=1.282×0.5×0.5nn=1.2822×0.250.042 &# ... See the full answer