Types of Group Designs
_________-subject design. The experiment compares
_____ group across different levels of the IV.
 e.g., behavior is studied in 1 group that is given placebo, low, medium, and high doses of alcohol.
Lect 10c 1

WITHIN-SUBJECTS DESIGNS
Within-subject design:
•
Sometimes called a _______________design
• _____ large group
• Random selection (usually)
• All subjects experience _____ conditions
• No _________________treatment
•
_______ exposure to conditions - no stability
• ___________ statistics used to analyze mean effects
• Subjects may not experience conditions in the same
______
• Can involve 2 or _____ levels of the IV
Lect 10c 2

Within-subject design, single factor
Group A:
Level 1 of IV
Group A:
Level 2 of IV


Same group examined under ____ levels of IV
Data usually analyzed used _____________
Lect 10c 3

Within-subject, multilevel-designs
Group A:
Level 1 of IV
Group A:
Level 2 of IV
Group A:
Level 3 of IV


Same group examined under ____________ of IV
Data usually analyzed used repeated-measures ______.
 Example: Craik and Tulving (1975) investigated whether different word-processing strategies affected memory. Asked questions before showing subjects words. Questions focused on visual properties, auditory properties, and semantic properties. (18%, 78%, 96%)
Lect 10c 4

How do within-subject design differ from a single-subject design?
 Single-subject design
1.
______ n
2.
3.
4.
5.
6.
Repeated measures within each condition
Conditions run until _____
Each participant’s behavior is evaluated against their
____ behavior under other conditions
Individualized treatment
______ analysis of data
 Within-subject design
1.
_______ n
2.
3.
4.
5.
6.
One measure under each condition
____ exposure to condition
A group’s average behavior under a condition is evaluated against the ____ group’s average behavior under other conditions
No individualized treatment
_____ analysis of data
Lect 10c 5

How do within-subject design differ from a single-subject design?
IV level 1
Subject
#1
IV level 1
Group
#1
IV level 2
Subject
#1
IV level 2
Group
#1
IV level 3
Subject
#1
IV level 3
Group
#1
Single-subject design
Within-subject design
Lect 10c 6

How do within-subject design differ from a between-subject design?
 Within-subject design
 Moderate n



____ group
A group’s average behavior under each condition is evaluated against the same group’s average behavior under other conditions
Between-subject design
 Large n


______ groups
Average behavior of a group exposed to one condition is evaluated against the average behavior of another group exposed to a different condition
Lect 10c 7

How do within-subject design differ from a between-subject design?
IV level 1
Group
#1
IV level 1
Group
#1
IV level 2
Group
#2
IV level 2
Group
#1
IV level 3
Group
#3
IV level 3
Group
#1
Between-subject design
Within-subject design
Lect 10c 8

WITHIN-SUBJECTS DESIGNS
Advantages of Within-subject designs over Betweengroup designs:
•
Main advantage ---Eliminates problems of individual
___________
• Individual differences between groups cannot confound the study
• You can measure treatment effects independent of individual differences
• Fewer _____________ than between group
Lect 10c 9

WITHIN-SUBJECTS DESIGNS
Disadvantages of Within-subject designs:
•
___________
• ______-related problems
• History, Maturation, Instrumentation, Statistical regression
• ________ effects – behavior may be influenced by earlier experiences in the study
1. __________ effects- changes in behavior caused by earlier treatment condition
2. __________________
– behavior changes as a function of experience - repeated testing (practice and fatigue)
Lect 10c 10

WITHIN-SUBJECTS DESIGNS-




Method of dealing with time-related threats
Subjects receive treatments in a ______ order

 e.g., Reverse counterbalancing: AB, BA e.g., Complete counterbalancing: In a study with 3 conditions (A, B, C) subjects may be exposed to:
ABC, ACB, CBA, CAB, BCA, or BAC
_____ numbers of participants get each possible sequence
Prevents order effects from __________________ particular condition
Lect 10c 11

No order effect
Treatment 1 Treatment 2
First
20
23
25
19
First
26
17
14
16
Mean =20
Second
27
29
29
26
Second
31
22
20
24
Mean =26
6 pt difference

No order effect
Treatment 1 Treatment 2
First
20
23
25
19
First
26
Second
27
29
29
26
Second
31
17
14
16
Mean =20
22
20
24
Mean =26
6 pt difference
Order effect (+ 5)
Treatment 1 Treatment 2
First
20
23
25
19
First
26
17
14
16
Mean =20
Second
32 (27+5)
34 (29+5)
34 (29+5)
31 (26+5)
Second
36 (31+5)
27 (22+5)
25 (20+5)
29 (24+5)
Mean =31
11 pt difference

Order effect without counterbalancing
Treatment 1 Treatment 2
First Second
20
23
32 (27+5)
34 (29+5)
25
19
First
26
17
14
16
Mean =20
34 (29+5)
31 (26+5)
Second
36 (31+5)
27 (22+5)
25 (20+5)
29 (24+5)
Mean =31
11 pt difference
Order effect with counterbalancing
Treatment 1 Treatment 2
First Second
20
23
32 (27+5)
34 (29+5)
25
19
Second
31 (26+5)
34 (29+5)
31 (26+5)
First
31
22 (17+5)
19 (14+5)
22
20
21 (16+5) 24
Mean =22.6
Mean =28.5
6 pt difference

Problems with counterbalancing
1.
2.
3.
Can increase _____________ within a treatment
Different treatments may produce different order effects
– _________________ order effects.
Complete counterbalancing requires ______________
 May use _____ counterbalancing to at least ensure that each condition is experienced by a group first, second, third, etc.
Lect 10c 15

Summary of Single-Factor (one IV)
Group Designs
1.
Between-subject designs
• 2 levels
• Multilevel
2. Control-group designs
• Pretest-posttest control group design
• Posttest only control group design
• Solomon 4-group design
3. Within-group designs
• 2 levels
• Multilevel
Lect 10c 16