According to Cappelleri and Darlington, (1994), Cohen Statistical Power Analysis is one of the most popular approaches in the behavioural sciences in calculating the required sampling size. According to Cohen (1998), in order to perform a statistical power analysis, five factors need to be taken into consideration:
1. significance level or criterion
2. effect size
3. desired power
4. estimated variance
5. sample size
Cohen (1988) statistical power analysis exploits the relationships among the five factors involved in statistical inferences. For any statistical model, these relationships are such that each is a function of the other four. Taking that into consideration, it means that if sample size is to be determined, it can be estimated for any given statistical test by specifying values for the other four factors: (1) significance level, (2) effect size, (3) desired power and (4) estimated variance.