Question

A company wants to estimate the mean length the machine is cutting the plastic within 0.125 inch. Determine the minimum sample size required to construct a 95% confidence interval for the population mean. Assume the population standard deviation is 0.25 inch.?

Answer 1

Solution :

Given that,

Population standard deviation = = 0.25

Margin of error = E = 0.125

At 95% confidence level the z is,

= 1 - 95%

= 1 - 0.95 = 0.05

/2 = 0.025

Z/2 = Z0.025 = 1.96  

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

n = [ 1.96 * 0.25 / 0.125 ]2

n = 15

Sample size = n = 15