Question

How to determine sample size for unknown population?

Answer 1

Where the population is unknown, the sample size can be derived by computing the minimum sample size required for accuracy in estimating proportions by considering the standard normal deviation set at 95% confidence level (1.96), percentage picking a choice or response (50% = 0.5) and the confidence interval (0.05 = ±5). The formula is:

n = z 2 (p)(1-p)

c 2

Where:

z = standard normal deviation set at 95% confidence level

p = percentage picking a choice or response

c = confidence interval