“…In the final design, one attribute had three levels, and the other three had two levels; thus, the total number of alternatives was 24 ( ). Based on the experience from the pilot study, presenting all alternatives to each participant may decrease response efficiency; a fractional factorial design using orthogonality was constructed by Ngene [ 30 ]. A set of 12 choice sets was selected based on orthogonality and grouped into four blocks, so the number of choices that each participant needed to complete was limited to three.…”