Define the objective of the study
Identify the population of interest
Choose the desired confidence level
Choose the acceptable margin of error
Estimate the population proportion or standard deviation
Determine the expected effect size
Set the statistical power
Select the significance level
Choose the sampling method
Use the appropriate sample size formula
For proportions: n = (Z² × p × (1 – p)) / E²
For means: n = (Z² × σ²) / E²
For finite populations: n_adjusted = n / (1 + (n – 1) / N)
Inflate for expected nonresponse or dropout
Round up to the next whole number
Verify the result with a sample size calculator or statistical software