“Patient dies due to hernia: Doctors in trouble” A study on the effect of framing and numerical information format on liability judgments

Purpose: We aimed to explore the effect of the way numerical information is framed on participants’ judgments. Specifically, based on a real story about a man who died after hernia surgery, we investigated the extent to which participants revised their liability judgment about the medical staff for not having used heparin, based first on ambiguous numerical information (relative risk reduction: 50%) and then on unambiguous numerical information (absolute risk reduction), that was framed either in terms of survival (e.g., 999 vs. 998 out of 1,000 patients survived) or mortality (1 vs. 2 out of 1,000 patients died), and presented as either resulting from small (1,000) or large (10,000) sample size groups. Method: Participants (N =160) were students (aged 19 to 45, M = 22.07, SD = 3.60) who volunteered to take part in the experiment. Perceived liability and perceived risk reduction were measured on 7-point scales. Result: When presented with relative risk information, participants judged the medical staff as more liable (M = 4.84, SE = .10) than when presented with absolute risk information (M = 4.22, SE = .11, F(1, 156) = 48.47, p = .0001, hp2= .24). The change in judged liability depended both on frame and on sample size, which did not interact: Participants’ rated the liability higher in the mortality condition (M = 4.76, SE = .13) than in the survival frame condition (M = 4.31, SE = .13) F(1, 156) = 5.61, p = .02, hp2 = .04 (and post-hoc analyses showed that the judgment was revised only in the survival condition), and participants’ ratings were lower in the small-1,000 size condition (M = 4.34, SE = .13) than in the large-10,000 size condition (M = 4.72, SE = .13) F(1, 156) = 3.89, p = .05, hp2 = .02. Participants’ estimates of perceived risk reduction were also affected both by the frame and the sample size as for liability. The results of mediational analyses were consistent with the hypothesis that perceived risk reduction plays a mediational role between the frame of information and the judgment of liability. Conclusion: Even when provided with unambiguous numerical information, people seem to be affected by the way in which it is framed, and the frame affects liability judgment through the perceived risk reduction.