Study characteristics including the proportion of studies reporting supported hypotheses
| Study characteristics | k | Proportion (95% CI) |
| Original research studies | 215 | – |
| Not reporting a study hypothesis | 86 | 40% (33.5% to 46.5%) |
| Reporting at least one study hypothesis | 129 | 60% (53.5% to 66.5%) |
| Original research studies reporting at least one study hypothesis | 129 | – |
| Stating an alternative primary hypothesis | 102 | 79.1% (72.0% to 86.1%) |
| Stating a null primary hypothesis | 19 | 14.7% (8.6% to 20.8%) |
| Stating both null and alternative hypotheses within the primary hypothesis | 8 | 6.2% (2.0% to 10.4%) |
| Original research studies reporting an alternative primary hypothesis | 102 | – |
| That state the direction of the hypothesis | 91 | 89.2% (83.2% to 95.2%) |
| That do not state the direction of the hypothesis | 11 | 10.8% (4.8% to 16.8%) |
| Is the primary hypothesis supported or rejected? | 129 | – |
| ‘Supported’ hypothesis | 106 | 82.2% (75.6% to 88.8%) |
| Rejected hypothesis | 23 | 17.8% (11.2% to 24.4%) |
| Is the supported primary hypothesis fully or partially supported? | 106 | – |
| Fully supported | 75 | 70.8% (62.1% to 79.4%) |
| Partially supported | 28 | 26.4% (18.0% to 34.8%) |
| Unclear | 3 | 2.8% (0.1% to 6.0%) |
k, number of studies.