where μ is the true mean and μ0 is the null mean or reference value. The difference between the actual value μ and the hypothesized value μ0 is the difference to detect. For the same significance level and power, a larger sample size is needed to detect a small difference than to detect a large difference. It is assumed that the population of interest is normally distributed with mean μ and standard deviation σ.
Figure 16.3 Initial Sample Size and Power Calculator for One Mean

Help created on 7/12/2018