1. Within-Subjects Design
Experimental Design

2. Between-Subjects Design (a. k. a., Independent Measures Design)
A research strategy in which scores are obtained from separate groups of participants in different conditions
EXPERIMENTAL GROUP
CONTROL GROUP

3. Within-Subjects Design (a.k.a., Repeated Measures Design)
Compares two or more conditions with scores obtained from the same group of participants
CONDITION 1
CONDITION 2

4. Advantages of Within-Subjects Designs
Eliminates Individual Differences*

5. CONDITION 1 CONDITION 2 John 20 Mary 30 Bill 40 Kate 50 MEAN 35 Sue 24
Tom 35
Dave 43
Ann 54
MEAN 39

6. CONDITION 1 CONDITION 2 John 20 Mary 30 Bill 40 Kate 50 MEAN 35 John24
Mary 35
Bill 43
Kate 54
MEAN 39

7. Advantages of Within-Subjects Designs
Eliminates individual differences *
Fewer Participants

8. Disadvantages of Within-Subject Designs
Environmental Variables
Setting, Time of Day, Weather, etc.

9. Disadvantages of Within-Subject Designs
Environmental Variables
Experience Variables
CARRYOVER EFFECTS
Changes in behavior or performance caused by participating in earlier treatments
PRACTICE
EFFECTS
FATIGUE
EFFECTS

10. NO CARRYOVER EFFECTS CARRYOVER EFFECTS
CONDITION 1
CONDITION 2
CONDITION 1
CONDITION 2 20 30 40 50
Mean = 35 19 25 41 55
Mean = 35 20 30 40 50
Mean = 35 25 35 45 55
Mean = 40
Some scores go up & some go down
All scores are +5

11. Counterbalancing
The order in which treatment conditions are administered from one participant to another are ordered to match with respect to time
CONDITION 1
CONDITION 2
Half of Participants
Half of Participants