Question

4) On a standard IQ test, σ = 15. How many random IQ scores must be obtained if we want to find the true population mean, with an allowable error of 0.5 and we want 99% confidence in the results?

5) Given n = 25, s = 15, and α = 0.01, find the maximum error of estimate, E.

Answer 1

4)

Given that,

Population standard deviation = = 15

Margin of error = E = 0.5

Z_/2 = 2.576

sample size = n = [Z_/2* / E] ²

n = [2.576 * 15 / 0.5]²

n = 5973

Sample size = n = 5973

5)

t _/2,df = 2.797

Margin of error = E = t_/2,df * (s /n)

= 2.797 * (15 / 25)

Margin of error = E = 8.391