Resumen

There is general agreement today that students should leave school with a good grasp of all the basic mathematical ideas about how to deal with uncertainty. As adults, they will have to make important decisions about the probability of certain events and about the risk of a wide range of dangers. The understanding of uncertainty also plays a central role in modern science. Many scientific discoveries of great importance would have been impossible if scientists had only conceived of the world in terms of certainty. In many situations studied by scientists, and most certainly in all situations studied in social sciences, researchers can at best identify and measure imperfect associations between variables. This paper summarises research about understanding correlations, which assess whether, how variables and the degree to which variables show a mutual association. The cognitive demands of understanding these associations are analysed and a brief review of the literature is presented.