Tankefel, vad är oddsen för det - En studie om konjunktionsfel bland konsumenter inom vadhållning på sportspel

Sammanfattning: Several studies have shown that people misjudge and fail to correctly combine probabilities. An explanation for these tendencies is the conjunction fallacy. Basically, the conjunction fallacy refers to violations of the conjunction rule, which states that the probability of a combination of two independent events (A & B) cannot exceed the probability of neither event (A or B). In connection with the growth of the Swedish gambling market and the fact that betting is an everyday-event containing well-defined probabilities, it is considered to be both up-to-date and relevant to study whether the conjunction fallacy also occurs in betting. Previous studies have shown that people fall victims of the conjunction error, however, only in controlled laboratory settings. This paper aims to empirically examine this phenomenon under more realistic circumstances. Choice behaviour of 240 experienced bettors was collected using experiments. Each bettor was asked to make a real-money choice between two types of bets with identical odds: a single bet and a multiple bet. The experiments were manipulated in regard to two variables: the level of odds (low vs. high) and information about the matches of the bets (presence vs. absence). The bettors also answered to a test aimed to measure the ability to understand and use probabilities. The participating bettors picked to a greater extent the multiple bets, indicating evidence for the conjunction fallacy. The manipulated variables had effects on the observed choice behaviour, while the test was unrelated to behaviour. The fact that a real choice between two authentic betting coupons was made in the experiment strengthens our results. Hence, consumers are prone to make the conjunction fallacy in everyday purchasing situations.