Ratio Bias Across Cultures and Disciplines: How Academic Background Shapes Statistical Decision-Making

Abstract

Ratios are an instrumental component of the communication of probabilities such as COVID incidence rates, side effects of medical drugs, or political decision-making; hence, they are a critical component of an individual's statistical decision-making. Research on the ratio bias has shown inconsistent results based on six major shortcomings which we surmount by replicating an identical experiment with students in Germany, Turkey, and Italy, with a physical, textual, and graphical depiction, and accounting for different levels of exposure to probabilities. In six studies (N = 1338), we show that lower exposure to probabilities leads to significantly more ratio bias–conform choices. The results also suggest that higher levels of statistical numeracy and risk literacy reduce ratio bias–conform choices. Our contribution helps to better understand the ratio bias concerning different populations and highlights different baselines for ratio bias–conform choices among subgroups in the population.