Question

Ari wants to find the average time Statistics students spend on homework. How large a sample should she take if she wants her error to be no more than 0.17 hours? sigma = 0.85 hours. Use 85% confidence interval.

Answer 1

Solution :

Population standard deviation = = 0.85

Margin of error = E = 0.17

At 85% confidence level

= 1-0.85% =1-0.85 =0.15

/2 =0.15/ 2= 0.075

Z/2 = Z0.075 = 1.44

Z/2 = 1.44

sample size = n = [Z/2* / E] 2

n = [ 1.44 *0.85 /0.17 ]2

n = 52

Sample size = n = 52