The experience-based format of probability improves probability estimates: The moderating role of individual differences in numeracy

People with low statistical numeracy have difficulties understanding numerical information. For instance, they often misunderstand the probability of experiencing side effects, which could reduce adherence to medical treatments. We investigated whether presenting information about probability using a method based on the direct experience of events influences the accuracy of probability estimates compared to viewing a static numerical description of the same information. Participants completed a numeracy test and were randomly assigned to one of two conditions. In the description-based probability condition, participants were presented with 24 binomial distributions consisting of a target stimulus “X” and a distractor stimulus “·” in the form of odds (the distribution “7 × 13 ·” is an example of a 35% probability: here the target [distractor] stimulus was present 7[13] times in a 20-stimulus distribution). In the experience-based probability condition, participants observed the same information but the stimuli were randomly arranged and displayed sequentially. Participants in both conditions estimated the probability of the target stimulus in each trial. In the experience-based format participants with low numeracy made more accurate probability estimates in comparison to the description-based format. In contrast, accuracy in participants with high numeracy was similar in the two formats.