Table 4 Overview of the experimental design and conduct of included studies
Aspect | Specification | Number of studies (%)b |
|---|---|---|
Type of design | Fractional factorial design | 35 (83.3) |
Full factorial design | 1 (2.4) | |
Not reported | 6 (14.3) | |
Design plan | Main effects | 2 (4.8) |
Main and interaction effects | 23 (54.8) | |
Not reported, main effects in primary analysis | 13 (31.0) | |
Not reported, main & interaction effects in primary analysis | 1 (2.4) | |
Not reported, unclear in analysis | 3 (7.1) | |
Software/approach, of studies reporting type of design (n = 36)a | Ngene | 9 (25.0) |
SAS | 3 (8.3) | |
Sawtooth | 3 (8.3) | |
SPSS | 2 (5.6) | |
Other computer algorithm | 3 (8.3) | |
Catalog approach | 5 (13.9) | |
Manual | 1 (2.8) | |
Other approach | 2 (5.6) | |
Not reported | 8 (22.2) | |
Piloting | Yes | 34 (81.0) |
No | 1 (2.4) | |
Not reported | 7 (16.7) | |
Mode of administration | Interview-administered | 5 (11.9) |
Self-administered | 34 (81.0) | |
Both | 1 (2.4) | |
Not reported | 2 (4.8) | |
Sample size | <  200 | 1 (2.4) |
200–400 | 14 (33.3) | |
400–600 | 12 (28.6) | |
600–800 | 6 (14.3) | |
800–1000 | 2 (4.8) | |
1000–1200 | 1 (2.4) | |
≥ 1200 | 6 (14.3) | |
(Financial) compensation | Yes | 15 (35.7) |
No | 2 (4.8) | |
Not reported | 25 (59.5) |