Suppose the U.S. president wants an estimate of the proportion of the population

Question

Suppose the U.S. president wants an estimate of the proportion of the population who support his current policy toward revisions in the health care system. The president wants the estimate to be within 0.03 of the true proportion. Assume a 90% level of confidence. The president's political advisors estimated the proportion supporting the current policy to be 0.07. (Use z Distribution Table.)

How large of a sample is required? (Round up your answer to the next whole number.)

How large of a sample would be necessary if no estimate were available for the proportion supporting current policy? (Round up your answer to the next whole number.)

How large of a sample is required? (Round up your answer to the next whole number.)

Explanation / Answer

You take (0.07) x (1 – 0.07) = 0.0651

Z score for 90% = 1.645

(1.645 / 0.03)^2 = 3007

(0.0651) x (3007) = 195.73 = 196

Second answer

You just use an estimate of .50 if they don’t give you one. So you take (.50) x (1-.50) = 0.25

(1.645 / 0.03)^2 = 3007

(0.25) X 3007 = 751.75 = 752

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