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AP Statistics Section 4.3 Types of Association
Objective: To be able to identify different types of association. Diagram notes: • Use a solid line for causation. • Use a dashed line for association. • We don’t always have to have both lines between variables. 1. Causation: a direct cause and effect relationship exists between x and y. Ex. Ibuprofen & pain relief • The best way to observe a cause and effect relationship is through the use of a well designed experiment.
Common response: the observed association between x and y is explained by a lurking variable z. Both x and y change in response to z. Ex. Grades in school and SAT scores • Confounding: the effects on the response variable can’t be distinguished between the explanatory variable(x) and the lurking variable(z). Ex. Time spent exercising and body weight
Establishing Causation without an Experiment (must have all 5) • Strong association • Association is consistent • Larger values of the explanatory variable are associated with larger values of the response variable • Alleged cause precedes the effect in time • Alleged cause is plausible