Mediation Analysis Sample Size Calculator
Mediation analysis is a statistical method used to understand the relationship between an independent variable, a dependent variable, and a mediator variable. The sample size calculator here helps you determine the appropriate sample size for your mediation analysis, ensuring your study has sufficient power to detect meaningful effects.
How to Use This Calculator
- Enter the desired sample size (n) in the first input field.
- Specify the significance level (α) in the second input field. This is typically set at 0.05.
- Enter the desired power (1 – β) in the third input field. A common choice is 0.80.
- Click the “Calculate” button. The calculator will display the required sample size and a power curve chart.
Formula & Methodology
The calculator uses the formula for sample size calculation in mediation analysis, as proposed by Fritz and MacKinnon (2007). The formula is based on the non-centrality parameter, which is a function of the effect sizes, the significance level, and the desired power.
Real-World Examples
Data & Statistics
| Effect Size (f) | Power (1 – β) |
|---|---|
| 0.2 | 0.32 |
| 0.5 | 0.80 |
| 0.8 | 0.99 |
Expert Tips
- Always round up the calculated sample size to the nearest whole number.
- Consider using a power analysis to determine the required sample size before starting your study.
- Be aware that the calculator assumes a two-tailed test and a medium effect size (f = 0.5).
Interactive FAQ
What is mediation analysis?
Mediation analysis is a statistical method used to understand the relationship between an independent variable, a dependent variable, and a mediator variable.
What is the significance level (α)?
The significance level (α) is the probability of rejecting the null hypothesis when it is true. It is typically set at 0.05.
For more information, see the Fritz and MacKinnon (2007) paper on sample size calculation in mediation analysis.