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ASSIGNING PARTICIPANTS TO CONDITIONS

ASSIGNING PARTICIPANTS TO CONDITIONS. Between-Subject designs Different people at each level of the IV X A : P 1 , P 2 , P 3 X B : P 4 , P 5 , P 6 Advantage Exposure to one level can’t contaminate performance on the other(s) Disadvantage

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ASSIGNING PARTICIPANTS TO CONDITIONS

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  1. ASSIGNING PARTICIPANTSTO CONDITIONS • Between-Subject designs • Different people at each level of the IVXA: P1, P2, P3XB: P4, P5, P6 • Advantage • Exposure to one level can’t contaminate performance on the other(s) • Disadvantage • Groups may not be equivalent, even with “random” assignment

  2. Within-Subject designs • Same people receive each level of the IVXA: P1, P2, P3XB: P1, P2, P3 • Advantages • More efficient • Each S serves as their “own control” • Eliminates subject variance from stats • Disadvantages • Exposure to one condition may influence performance in others • Order and carryover effects

  3. Counterbalancing • Blocked designs • Order of conditions is varied over participants • Complete counterbalancing: Subgroup 2 IV levels 3 IV levels etc. 1 AB ABC2 BA ACB 3 BAC 4 BCA 5 CAB5 CBA

  4. Complete counterbalancing (contd) • Advantages • Controls for order effects; each level appears at each order same amount • Allows for order effects to be assessed • Disadvantages • Back to multiple “groups” and inefficiency • Doesn’t control for “asymmetric transfer”

  5. Latin Square Designs • Put each level in each position, counterbalancing order and sequenceSubgroup 1st 2nd 3rd 4th 1 A B C D 2 B D A C 3 D C B A 4 C A D B • Advantage • Much more efficient than complete counterbalancing • Disadvantages: • May miss complex order effects • Still doesn’t control for asymmetric transfer

  6. Counterbalancing • Repeated Block Designs • Each participant gets two (or more) blocks of each condition, intermixed • ABBA designs • ABBA / BAAB designs • Completely randomized block designs • AABABCCBABAAB….. • May be effects of random vs. blocked

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