Question

It is known that the population variance equals 529. With a .95 probability, the sample size that needs to be taken if the desired margin of error is 4 or less is?

a. 128

b. 127

c. 509

d. 508

Answer 1

Solution :

variance = ² = 529

standard deviation = = ² = 529 = 23

margin of error = E = 4

Z_/2 = Z_0.025 = 1.96  

sample size = n = [Z_/2* / E] ²

n = [ 1.96 * 23 / 4 ]²

n = 127.01

Sample size = n = 128

correct option is a