Calculate Sample Size Using Power Analysis
Calculate sample size using power analysis is a crucial step in designing experiments and surveys. It ensures that your study has enough participants to detect an effect with a certain level of confidence.
- Enter the effect size, significance level (α), power, and standard deviation (SD) in the respective fields.
- Click the “Calculate” button.
- View the calculated sample size and chart below the calculator.
The formula used in this calculator is based on Cohen’s power analysis:
n = [(Z_α/2 + Z_β) / E]² * SD²
| Effect Size | Sample Size (n) |
|---|---|
| 0.2 | 1280 |
| 0.5 | 64 |
| 0.8 | 25 |
- Always round up the calculated sample size to ensure your study has enough power.
- Consider using a power analysis tool before starting your study to avoid wasting resources.
- Remember that power analysis is just one aspect of study design; other factors, such as recruitment and retention, are also crucial.
What is effect size?
Effect size is a measure of the magnitude of a phenomenon. In the context of power analysis, it’s the expected difference between two groups divided by the standard deviation.
For more information, see these authoritative sources:
CDC’s Guide to Sample Size Calculation Penn State’s Power Analysis Tutorial