Equivalence Trial Sample Size Calculator
Equivalence Trial Sample Size Calculation Table
| Factor | Description |
|---|---|
| Objective | Demonstrate that two treatments are clinically equivalent. |
| Equivalence Margin (Δ) | The maximum acceptable difference (e.g., ±5%) between treatments. |
| Significance Level (α) | Typically 0.05 (5%) for a two-sided test. |
| Power (1-β) | Probability of detecting equivalence if it exists (e.g., 80% or 90%). |
| Standard Deviation (σ) | Estimated from prior studies or pilot data. |
| Allocation Ratio (r) | Ratio of sample sizes between groups (e.g., 1:1 or 2:1). |
| Formula | n=2σ2(Z1−α/2+Z1−β)2Δ2n = \frac{2\sigma^2 (Z_{1-\alpha/2} + Z_{1-\beta})^2}{\Delta^2}n=Δ22σ2(Z1−α/2+Z1−β)2 |
| Sample Size Increase Factors | - Lower equivalence margin requires a larger sample. - Higher power increases required sample size. - Larger variance requires a bigger sample. |
| Software & Tools | - PASS - G*Power - SAS - R ( power.TOST function) |