Kahneman and Tversky in 1971, conducted a study to assess the intuitive understanding of sampling affects among statisticians. After asking the statisticians:

• There are two hospitals, one large and one small. 60% of the babies born in one of the hospitals on a specific day happened to be a boy. Which hospital was it likely to be?

During a causal conversation, most statisticians answered wrong and chose the large hospital. This is despite the fact a basic idea in statistics is that small sample sizes are likely to be variable. The context the idea was expressed in caused errors among "experts" in the discipline.