Table 2 Relative power of t-test and Mann-Whitney given as relative efficiency. Values less than 1 indicate greater power of t-test; greater than 1 indicates superiority of Mann-Whitney. Results are combined across sample sizes and correlations.
Distribution | Post-treatment scores | Change scores |
|---|---|---|
Moderate positive skew: shift | 0.9348 | 0.9835 |
Moderate positive skew: ratio | 1.1382 | 1.0436 |
Moderate negative skew: shift | 1.1833 | 1.0187 |
Moderate negative skew: ratio | 0.9301 | 0.9825 |
Uniform: shift | 0.9339 | 0.9846 |
Uniform: ratio | 0.9488 | 0.9929 |
Extreme negative skew: shift | 1.3769 | 1.1140 |
Extreme negative skew: ratio | 1.6675 | 1.2046 |
Extreme asymmetry: shift | 7.1461 | 0.5370 |
Extreme asymmetry: ratio | 9.0091 | 0.6432 |
Normal: shift | 0.9660 | 0.9726 |
Normal: ratio | 0.9740 | 0.9760 |