Question

Which of the following best represents the appropriate sample size to use when estimating an unknown population mean within 3 units, with 80% confidence if an estimate of the population standard deviation is 12?

A 7
B		27
C		44
D		62

Answer 1

Solution :

Given that,

standard deviation = = 12

margin of error = E = 3

At 80% confidence level the z is ,

= 1 - 80% = 1 - 0.80 = 0.20

/ 2 = 0.20 / 2 = 0.10

Z_/2 = Z _0.10 = 1.28

Sample size = n = ((Z_/2 * ) / E)²

= ((1.28 * 12) / 3)²

= 27

Sample size = 27

option B is correct