1 MINIPROJECT REPORT Undoing the side-effects of statistics education. – Developing training methods to eliminate the equiprobability bias.

This project was aimed at finding ways of eliminating the equiprobability bias (Lecoutre, 1985) which is a tendency for individuals to think of random events as “equiprobable ” by nature, and to judge outcomes that occur with different probabilities as equally likely. The project was based on a large scale study (Morsanyi, Primi, Chiesi & Handley, 2009) which showed that, paradoxically, psychology students at more advanced stages of their education tend to give more incorrect equiprobability responses than students who had no former education in statistics. The aim of the project was to develop and compare training methods that can eliminate the bias, and thus undo the side-effects of statistics education. The training methods were based on three different theoretical approaches: Lecoutre’s (1985) theory of the equiprobability bias, the theory of naïve probability (Johnson-Laird, Legrenzi, Girotto, Sonino-Legrenzi & Caverni, 1999), and the fast and frugal heuristics approach (e.g., Gigerenzer, Gaissmaier, Kurz-Milcke, Schwartz, & Woloshin, 2008). The study was conducted with first, second and third year psychology students from the University of Plymouth. The students either took part in one of three training sessions (experiments with random generators, training in extensional reasoning, statistics in real life) which was followed by filling in a probabilistic reasoning questionnaire, or they took part in the study as a control group (i.e., they just filled in the questionnaire). Students ’ cognitive capacity, and their need for cognition were also measured. The results indicated that the random generators training successfully decreased the equiprobability bias. However, none of the trainings increased overall normative responding on the questionnaire (some tasks measured heuristics and biases other than the equiprobability bias). Nevertheless, a post-training questionnaire indicated that students enjoyed the training sessions and found them useful