Question

You want to obtain a sample to estimate a population mean. Based on previous evidence, you believe the population standard deviation is approximately σ=59.2. You would like to be 98% confident that your estimate is within 10 of the true population mean. How large of a sample size is required?

n = __________________

Answer 1

Solution :

Given that,

standard deviation =s =   =59.2

Margin of error = E = 10

At 98% confidence level the z is ,

= 1 - 98% = 1 - 0.98 = 0.02

/ 2 = 0.02/ 2 = 0.01

Z/2 = Z0.01 = 2.326 ( Using z table    )

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

n = ( 2.326* 59.2 / 10 )2

n =189.6

Sample size = n =190