The validity of person tradeoff measurements: randomized trial of computer elicitation versus face-to-face interview

Can person tradeoff (PTO) value judgments be elicited by a computer, or is a face-to-face interview needed? The authors randomly assigned 95 subjects to interview or computer methods for the PTO, a valuation measure that is often difficult for subjects. They measured relative values of foot numbness, leg paralysis, and quadriplegia (all 3 pairs) at 2 reference group sizes (10 or 100). Relative values did not differ between computer and interview. Overall, 21% of responses were equality responses, 13% were high extreme values, and 5% violated ordinal criteria. The groups did not differ in these measures. The authors also assessed consistency across reference group size (10 v. 100). Although relative values were significantly lower for 100 than for 10, mode did not influence the size of this effect. Subjects made, on average, equally consistent judgments for the 3 comparisons. A computerized PTO elicitation protocol produced results of similar quality to that of a face-to-face interview.