Question

Find the sample size, n, needed to estimate the mean of a normal population, μ, with σ = 9.25 and a maximum error of E = 3.2 at a 99% level of confidence.

Answer 1

Solution :

Given that,

standard deviation =   =9.25

Margin of error = E = 3.2

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.58

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

n = ( 2.58* 9.25/ 3.2)2

n =55.61

Sample size = n =56