HANDOUT 10.1


THE LOGIC OF CAUSALITY


SIMPLE EXPERIMENT IN PSYCHOLOGY PHYSICS EXPERIMENT


MAKE SURE SUSPECTED CAUSE (TREATMENT) COMES BEFORE EFFECT. WE INTRODUCE INDEPENDENT VARIABLE AND THEN LATER MEASURE DEPENDENT VARIABLE. MAKE SURE SUSPECTED CAUSE (TREATMENT) COMES BEFORE EFFECT.
DETERMINE WHETHER BEHAVIOR CHANGE COMES AFTER INTRODUCING THE TREATMENT. THIS IS WHY WE COMPARE THE EXPERIMENTAL GROUP'S BEHAVIOR WITH THE CONTROL GROUP'S. DETERMINE WHETHER BEHAVIOR CHANGE COMES AFTER INTRODUCING THE TREATMENT
MAKE SURE THAT NO OTHER FACTORS COULD CAUSE THE BEHAVIOR CHANGE BY (1) RANDOM ASSIGNMENT TO ENSURE THAT THE INDEPENDENT VARIABLE IS THE ONLY VARIABLE THAT SYSTEMATICALLY VARIES. ALL OTHER VARIABLES VARY RANDOMLY. AND BY (2) USING STATISTICAL TESTS TO TRY TO RULE OUT THE LIKELIHOOD THAT THE DIFFERENCE BETWEEN GROUPS IS DUE TO THE EFFECTS OF RANDOM VARIABLES. MAKE SURE THAT NO OTHER FACTORS COULD CAUSE THE EFFECT BY ELIMINATING ALL EXTRANEOUS VARIABLES. THE ONLY FACTOR ALLOWED TO VARY IN THE EXPERIMENT IS THE TREATMENT. ALL OTHER NON-TREATMENT FACTORS ARE HELD CONSTANT.

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