Presents a classroom demonstration illustrating the connection between spread and Pearson's r. Discusses different factors that may result in an increase, decrease, or no change in r. Describes an exercise using decks of playing cards to generate hypothetical data on variables of intelligence quotient (IQ) and grade point average (GPA). (DK)

Described is an activity designed to make the concepts of experimentation, independent variables, and dependent variables easy to understand by using observable characteristics of several rods to illustrate these concepts. (DS)