=+13.21 ● The accompanying data were read from a plot

(and are a subset of the complete data set) given in the article “Cognitive Slowing in Closed-Head Injury” (Brain and Cognition [1996]: 429–440). The data represent the mean response times for a group of individuals with closed-head injury (CHI) and a matched control group without head injury on 10 different tasks. Each observation was based on a different study, and used different subjects, so it is reasonable to assume that the observations are independent.