MedicalResearch.com: What is the background for this study? What are the main findings?
- More than 20 years ago, Gigerenzer and Hoffrage (1995) were able to show the advantages of so-called natural frequencies (e.g., 8 out 10 women) compared to probabilities expressed with percentages (e.g. 80% of the women) when it comes to solving Bayesian reasoning problems. Only last year, a meta-analysis (McDowell & Jacobs, 2017) revealed that while only 4% of all people are able to solve such a task in probability format, tasks that are presented in natural frequencies have solution rates of 24%. Even though this improvement is remarkable, still more than three quarters of participants fail with the intuitive natural frequencies. We wanted to know what exactly these people did wrong.In a first step, we checked the questionnaires from previous studies (e.g. Binder, Krauss, & Bruckmaier, 2015) and found out that many participants had translated given frequencies into probabilities. In a second step, we wanted to examine this systematically.
- With our study, we were able to show that many people actually do not actively make use of the intuitive natural frequencies when presented with a task in frequency format. Instead, they rely on the more complex probabilities, with which they are more familiar from their mathematics education. As a consequence, the majority of these people who translate the intuitive frequencies into more complex probabilities cannot solve the task any more.