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Table 4 Overview of the experimental design and conduct of included studies

From: Vaccine preferences driving vaccine-decision making of different target groups: a systematic review of choice-based experiments

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)
  1. aNote that the proportion of the studies using particular software packages or approaches is taken from the studies reporting their type of design (n = 36) instead of all includes studies (n = 42); bDue to rounding of percentages, the total may not count up to 100%