Table 1. Variance comparison.
Alternative possible methods to estimate the number and percentage of studies with different variances on comparisons between arms and over-time. Limits for declaring different variances come from different statistical methods; either masked specified statistical tests (F for independent outcomes or Sachs’ test 18 for related samples); or sensitivity analysis about the number of studies that have to be deleted from the random mixed model in order to achieve a negligible heterogeneity (see Methods for details). ¥ Only performed in studies reporting enough information to obtain the variability of the change from baseline to outcome, for example because they provide the correlation.
| Comparing variances | N | Method | After treatment, variability is… | ||
|---|---|---|---|---|---|
| Increased
n (%) |
Decreased
n (%) |
Not changed
n (%) |
|||
| Outcome between
treatment arms |
208 | F test | 15 (7.2%) | 26 (12.5%) | 167 (80.3%) |
| Random model | 11 (5.3%) | 19 (9.1%) | 178 (85.6%) | ||
| Outcome versus
baseline in treated arm |
95 ¥ | Paired test | 16 (16.8%) | 22 (23.2%) | 57 (60.0%) |
| Random model | 13 (13.7%) | 19 (20.0%) | 63 (66.3%) | ||