The sample size evaluation primarily depends on the study design and the outcome which is estimated prior to the start of the study. ... The factors affecting sample sizes are study design, method of sampling, and outcome measures – effect size, standard deviation, study power, and significance level.

What does sample size depend on?

Sample size is mainly determined by the sample design, required accuracy of estimates, and resource constraints. For a particular design, sample size can be determined by the level of accuracy required, or confidence interval at a given confidence level desired (Cochran, 1977: 75–78).

What factors determine a sample size?

In general, three or four factors must be known or estimated to calculate sample size: (1) the effect size (usually the difference between 2 groups); (2) the population standard deviation (for continuous data); (3) the desired power of the experiment to detect the postulated effect; and (4) the significance level.