Calculating the required sample size ensures your survey results are statistically valid.
Formula
We use the standard formula for a finite population (though usually population is assumed infinite):
n = (Z² * p * (1-p)) / e²
- Z: Z-score (1.96 for 95% confidence)
- p: Expected proportion (usually 0.5 for maximum variability)
- e: Margin of Error (e.g., 0.05 for ±5%)