From: Variety in mental health research data: when does more become too much?
 | Domains | Number of different variables/instruments | Use per type of study | Total (average use per variable/instrument) | |||||
---|---|---|---|---|---|---|---|---|---|
 |  |  |  | Effect (N = 46) | Other (N = 46) |  |  | ||
Variables | Â | Â | Â | Â | Â | Â | Â | Â | Â |
 | Demographic | 30 | 24% | 74 | 37% | 67 | 43% | 141 (4.8) | 39% |
 | Diagnostic | 51 | 41% | 59 | 30% | 47 | 30% | 106 (2.2) | 30% |
 | Treatment/intervention | 39 | 31% | 63 | 32% | 43 | 27% | 106 (2.8) | 30% |
 | Effect | 4 | 3% | 4 | 2% | 0 | 0% | 4 (1) | 1% |
 | Total | 124 | 100% | 200 | 100% | 157 | 100% | 357 (3.1) | 100% |
Instruments | Â | Â | Â | Â | Â | Â | Â | Â | Â |
 | Demographic | 0 | 0 | 0 | 0 |  |  |  |  |
 | Diagnostic | 112 | 50% | 59 | 25% | 78 | 60% | 137 (1.2) | 37% |
 | Treatment/intervention | 1 | 0% | 0 | 0% | 1 | 1% | 1 (1) | 0% |
 | Effect | 110 | 49% | 177 | 75% | 52 | 40% | 229 (2.1) | 62% |
 | Total | 223 | 100% | 236 | 100% | 131 | 100% | 367 (1.6) | 100% |