Impact of discussion on preferences elicited in a group setting.
BACKGROUND
The completeness of preferences is assumed as one of the axioms of expected utility theory but has been subject to little empirical study.


METHODS
Fifteen non-health professionals was recruited and familiarised with the standard gamble technique. The group then met five times over six months and preferences were elicited independently on 41 scenarios. After individual valuation, the group discussed the scenarios, following which preferences could be changed. Changes made were described and summary measures (mean and median) before and after discussion compared using paired t test and Wilcoxon Signed Rank Test. Semi-structured telephone interviews were carried out to explore attitudes to discussing preferences. These were transcribed, read by two investigators and emergent themes described.


RESULTS
Sixteen changes (3.6%) were made to preferences by seven (47%) of the fifteen members. The difference between individual preference values before and after discussion ranged from -0.025 to 0.45. The average effect on the group mean was 0.0053. No differences before and after discussion were statistically significant. The group valued discussion highly and suggested it brought four main benefits: reassurance; improved procedural performance; increased group cohesion; satisfying curiosity.


CONCLUSIONS
The hypothesis that preferences are incomplete cannot be rejected for a proportion of respondents. However, brief discussion did not result in substantial number of changes to preferences and these did not have significant impact on summary values for the group, suggesting that incompleteness, if present, may not have an important effect on cost-utility analyses.
Stein
Ken
K
Peninsula Technology Assessment Group, Peninsula Medical School, University of Exeter, Exeter, EX2 5DW, UK. ken.stein@exeter.ac.uk
Ratcliffe
Julie
J
Round
Ali
A
Milne
Ruairidh
R
Brazier
John E
JE
D000368:Aged; D000369:Aged, 80 and over; D001294:Attitude to Health; D032921:Consensus; D003258:Consumer Behavior; D003657:Decision Making; D005260:Female; D005715:Gambling; D006075:Governing Board; D006126:Group Processes; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D017008:Negotiating; D017063:Outcome Assessment, Health Care; D011320:Primary Health Care / Q000458:organization & administration*; D012945:Social Values; D013222:State Medicine; D014341:Trustees / Q000523:psychology* / Q000706:statistics & numerical data; D006113:United Kingdom