Question

Let’s say we need to study a sample and be 99% confident that the sample’s mean will be within 0.72 units of the population’s true mean. If the population standard deviation is 3.40 units, what is the minimum sample size that we should use?

Answer 1

Solution :

Given that,

standard deviation = σ =3.40

Margin of error = E = 0.72

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 *  σ/ E]2

n = ( 2.576*3.40 /0.72 )2

n =147.9

Sample size = n =148