The two items specifically assessing willingness to participate were also scored on the same 4-point Likert scale as the attitudinal items. One was positively worded (‘I would be willing to participate in genetic research’) and the other was negatively worded (‘I would not be willing to participate in genetic research’). We selected the negatively worded item as our outcome variable of interest because it correlated more strongly with the other items, and yielded a higher response variance (0.91 vs. 0.86), than its positively worded counterpart, which enabled superior differentiation among respondents. We reverse-scored this item for further analyses.
