Predictability and the Base Rate

Whenever a statistician wants to predict the likelihood of some event based on the available evidence, there are two main sources of information that have to be taken into account: (1) the evidence itself, for which a reliability figure has to be calculated; and (2) the likelihood of the event calculated purely in terms of relative incidence. The second figure here is the base rate. Since it is just a number, obtained by the seemingly dull process of counting, it frequently gets overlooked wh...

 Preschool Social Programs Demonstrate the Importance of a...

In 1962, researchers wanted to test the effects of an early-childhood preschool training program they had designed. Kids in Ypsilanti, Michigan, were randomly assigned to one of two groups. The first attended the preschool program (which eventually became a model for other preschool programs nationwide, including Head Start). The second group did not. The differences powerfully illustrate the importance of a child’s early years. The kids in the program academically outperformed the contro...