A survey by the AARP ( Money , June 2007) reported that approximately 70% of peo

Question

A survey by the AARP (Money, June 2007) reported that approximately 70% of people in the 50 to 64 age bracket have tried some type of alternative therapy (for instance, acupuncture or the use of nutrition supplements). Assume this survey was based on a sample of 400 people. Use Table 1.

Compute the point estimate as well as the margin of error with 90% confidence. (Round intermediate calculations to 4 decimal places, "z" value and “point estimate” to 2 places, and "margin of error" to 3 decimal places.)

You decide to redo the analysis with the margin of error reduced to 2%. How large a sample do you need to draw? (Round intermediate calculations to 4 decimal places and "z" value to 2 decimal places. Round up your answer to the nearest whole number.)

A survey by the AARP (Money, June 2007) reported that approximately 70% of people in the 50 to 64 age bracket have tried some type of alternative therapy (for instance, acupuncture or the use of nutrition supplements). Assume this survey was based on a sample of 400 people. Use Table 1.

Explanation / Answer

a1)The parameter of interest is the proportion of all people between the ages of 50-64.

a-2. Point estimate p=0.70

here std error =(p(1-p)/n)1/2 =0.0229

for 90% CI; z=1.6449

Margin of error =z*std error =0.0377

b)margin of error E =0.02

sample size =p(1-p)*(Z/E)2 =1421

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