There are various methods and formulas to calculate sample size, depending on the type of study and data. Some common methods include:
For proportions (e.g., prevalence studies): Use the formula \( n = \frac{Z^2 \cdot P(1-P)}{d^2} \), where \( n \) is the sample size, \( Z \) is the Z-value (e.g., 1.96 for 95% confidence), \( P \) is the estimated proportion, and \( d \) is the desired precision. For means (e.g., comparing means between two groups): Use the formula \( n = \frac{2 \cdot \sigma^2 \cdot (Z_{\alpha/2} + Z_{\beta})^2}{\Delta^2} \), where \( \sigma \) is the population standard deviation, \( Z_{\alpha/2} \) and \( Z_{\beta} \) are the Z-values for the significance level and power, and \( \Delta \) is the expected mean difference.
