Table 2.
Characteristic | All studies (k = 100) | Published studies (k = 17) | Unpublished studies (k = 83) |
---|---|---|---|
Design | |||
Between-subjects RCT | 72 (72%) | 16 (94%) | 56 (67%) |
Within-subject RCT | 1 (1%) | 1 (6%) | 0 (0%) |
Cluster RCT | 2 (2%) | 0 (0%) | 2 (2%) |
Between-subjects NRCT | 21 (21%) | 0 (0%) | 21 (25%) |
Within-subject UCT | 4 (4%) | 0 (0%) | 4 (5%) |
Outcome measurement | |||
Direct behavioral measure | 2 (2%) | 1 (6%) | 1 (1%) |
Self-reported past behavior | 41 (41%) | 1 (6%) | 40 (48%) |
Intended future behavior | 57 (57%) | 15 (88%) | 42 (51%) |
Percent missing data | 7.5 (7.3, 42) | 0 (0, 7.95) | 13.2 (7.5, 59.75) |
Not reported | 23 (23%) | 2 (12%) | 21 (25%) |
Exchangeability | |||
Low risk of bias | 52 (52%) | 16 (94%) | 36 (43%) |
Medium risk of bias | 9 (9%) | 1 (6%) | 8 (10%) |
High risk of bias | 29 (29%) | 0 (0%) | 29 (35%) |
Unclear | 10 (10%) | 0 (0%) | 10 (12%) |
Avoidance of social desirability bias | |||
Low risk of bias | 13 (13%) | 6 (35%) | 7 (8%) |
Medium risk of bias | 14 (14%) | 5 (29%) | 9 (11%) |
High risk of bias | 68 (68%) | 6 (35%) | 62 (75%) |
Unclear | 5 (5%) | 0 (0%) | 5 (6%) |
External generalizability | |||
Low risk of bias | 36 (36%) | 10 (59%) | 26 (31%) |
Medium risk of bias | 28 (28%) | 7 (41%) | 21 (25%) |
High risk of bias | 15 (15%) | 0 (0%) | 15 (18%) |
Unclear | 21 (21%) | 0 (0%) | 21 (25%) |
Preregistered | |||
Yes | 25 (25%) | 2 (12%) | 23 (28%) |
No | 75 (75%) | 15 (88%) | 60 (72%) |
Public data | |||
Yes | 53 (53%) | 5 (29%) | 48 (58%) |
No | 47 (47%) | 12 (71%) | 35 (42%) |
Public code | |||
Yes | 22 (22%) | 4 (24%) | 18 (22%) |
No | 78 (78%) | 13 (76%) | 65 (78%) |
Overall lowest risk of bias | |||
Yes | 12 (12%) | 9 (53%) | 3 (4%) |
No | 88 (88%) | 8 (47%) | 80 (96%) |
k: Number of studies in subset. RCT: randomized controlled trial. NRCT: non-randomized controlled trial. UCT: uncontrolled trial (i.e., no separate control group) but with subjects serving as own controls.
For studies in which missing data was unreported but the outcome was measured in the same session as the intervention, we coded missing data as 0. Details on the risk-of-bias categories are provided in the Supplement.