Table 2 Experimental design of included studies

Design plan

Main effects only

4 (14.8)

Main effects + interactions

1 (3.7)

Not clearly reported in text but main effects only in primary analysis

20 (74.1)

Not reported and unclear from analysis

2 (7.4)

Design source

SAS

11 (40.7)

Sawtooth Software

5 (18.5)

SPEED

3 (11.1)

IBM SPSS Statistics

2 (7.4)

Sloane’s orthogonal array

1 (3.7)

Not reported

5 (18.5)

Design of choice tasks

Orthogonal array (all using one constant comparator)

8 (29.6)

Efficient design

15 (55.6)

Not clearly reported

4 (14.8)

Number of choice tasks

<10

8 (29.6)

10-15

6 (22.2)

16-20

13 (48.1)