Question

Suppose that a quality control manager at Argon Chemical Company wishes to measure the average amount of cleaning fluid the company has placed. From previous studies, they believe their population standard deviation to be 0.39 oz. How large a sample must be taken in order to be 99% confident of estimating the mean cleaning fluid within 0.05oz?

Answer 1

Solution :

Given that,

standard deviation = =0.39

Margin of error = E = 0.05

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.576

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

n = ( 2.576*0.39 / 0.05)2

n =403.72

Sample size = n =404