Question

If the allowable error is given as a percent what measure of the population variation would you use to calculate sample size? Assume no calculation other than the sample size calculation.

Answer 1

Let

Margin of Error or Allowable Error = E ( Say Error is 3%, So E = 0.03)

Population Standard deviation =

sample size = n

and z be the critical value of z -score for a particular confidence level

Now, E = z * ( / )

Squaring both sides, we get

E² = z² * (² / n)

So, n = [ (z * ) / E]²

Hence we need Population standard deviation to calculate sample size