PPT Slide
USING INTERACTION EFFECTS TO RESOLVE CONTRADICTORY
FINDINGS FROM PREVIOUS SINGLE-FACTOR EXPERIMENTS
ASSUME THE FOLLOWING INTERACTION EFFECT IS OBTAINED IN A 2X2 FACTORIAL EXPERIMENT WITH STUDY METHOD AND INCENTIVE LEVEL AS THE
INDEPENDENT VARIABLES (CASE 3):
READ ONLY (A1) UNDERLINE (A2)
LOW INCENTIVE 18.50 14.50
HIGH INCENTIVE 14.50 18.50
THE DISCOVERY OF THIS INTERACTION EFFECT COULD EXPLAIN THE FOLLOWING CONTRADICTORY FINDINGS FROM PRIOR SINGLE-FACTOR EXPERIMENTS IN WHICH STUDY METHOD WAS MANIPULATED AND INCENTIVE LEVEL WAS CONTROLLED IN VARYING WAYS:
1. IF INCENTIVE LEVEL WAS HELD CONSTANT AT A LOW LEVEL: A1 > A2
2. IF INCENTIVE LEVEL WAS HELD CONSTANT AT A HIGH LEVEL: A1 <A2
3. IF INCENTIVE LEVEL WAS HELD CONSTANT AT A MEDIUM LEVEL OR
LOW AND HIGH LEVELS WERE BALANCED ACROSS GROUPS : A1 = A2