Table 3.
Frequencies and percentages of effect sizes by study characteristics.
| Study characteristic | Academic effect sizes (%) | Nonacademic effect sizes (%) |
|---|---|---|
| Experimental design | ||
| Posttest‐only with control group | 20/113 (17.7) | 20/91 (22.0) |
| Pretest‐posttest with control group | 79/113 (69.9) | 58/91 (63.7) |
| Matched pairs | 14/113 (12.4) | 39/91 (42.9) |
| Rationale for baseline equivalency | ||
| Nonstatistically significant pretest differences | 58/113 (51.3) | 55/91 (60.4) |
| Gain scores | 30/113 (26.5) | 46/91 (50.5) |
| Covariate‐adjusted means | 57/113 (50.4) | 32/91 (35.2) |
| Random assignment | 72/113 (63.7) | 15/91 (16.5) |
| Follow‐up at least 1 year after intervention | 37/113 (32.7) | 13/91 (14.3) |
| Public Montessori school | 76/107 (71.0) | 36/70 (51.4) |
| Public control‐group school | 60/108 (55.6) | 36/70 (51.4) |
| Standardized test used as measure | 71/113 (62.8) | 0/91 (0.0) |
| Grade level | ||
| Preschool or kindergarten | 36/113 (31.9) | 39/91 (42.9) |
| Elementary school | 44/113 (38.9) | 44/91 (48.4) |
| Middle school | 19/113 (16.8) | 8/91 (8.8) |
| High school | 14/113 (12.4) | 0/91 (0.9) |
| Geographic region | ||
| Asia | 5/113 (4.4) | 5/91 (5.5) |
| Europe | 8/113 (7.1) | 40/91 (44.0) |
| Middle East | 1/113 (0.9) | 0/91 (0.0) |
| North America | 99/113 (87.6) | 46/91 (50.5) |
| Peer‐reviewed publication | 81/113 (71.7) | 78/13 (85.7) |