Transcript Experimental Psychology - University of Richmond

Research Methods
Complex Designs
Lecture Outline
One-way Designs
Factorial Designs
Main effects
 Interactions

One-Way Designs
One-way refers to one independent variable
Two groups design

The simplest one-way design

One IV with 2 levels
Foot-in-the-door technique

Get person to consent to small task first, then ask for larger task
EXAMPLE: Freedman & Fraser (1966)
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
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Went door to door
Small request: Sign petition
Large request: Huge, ugly sign on lawn
Experimental group= small then large
Control group = large request only
Foot-in-the-Door
60
50
40
30
20
10
0
Large
request
only
Small then
large
More than two levels…
Several reasons you may want more than 2
levels of one IV
A) 2 levels cannot provide much information
about the exact relationship between IV and
DV
 B) 2 levels cannot detect curvilinear
relationships
 C) May be interested in more than 2 groups

A) Lack of Precise Information
Motivation and performance on a motor task
2 levels of reward
100
90
80
70
60
50
$0
$4
AMOUNT OF REWARD
A) Lack of Precise Information
Increased to five levels
Positive monotonic relationship
100
90
80
70
60
50
$0 $1 $2 $3 $4
AMOUNT OF REWARD
B) Curvilinear relationships
Nonmonotonic

Increases in the value of one variable are accompanied
by increases and decreases in values of another
.
DEPENDENT
VARIABLE
Fear and attitude change
High
Low
Level 1
Level 2
Level 3
C) Interested in More Than
Two Things
Effects of animal companionship on nursing home
residents

2 group design:


Dog / No Dog
More than 2 groups

Dog, Bird, Cat, No animal
Stress reducing techniques (Bruning & Frew, 87)

4 group design


Exercise, management skills training, medication, control
All 3 techniques decreased blood pressure and pulse
Increasing the IVs:
Factorial Designs
Factorial designs

More than one independent variable (or factor)
Number of levels X Number of levels X Number of levels
of first IV
of second IV
of third IV
Determining the number of conditions

2x3


3x3


6 conditions
9 conditions
2x2x2

8 conditions
A 2 x 2 Design
Head movement and persuasive arguments

Participants listened to a persuasive argument while
moving their head
Independent variables


Persuasive argument: Tuition increase or tuition
decrease
Head movement: Nod head or shake head
Conditions?

2x2= 4
A 2 x 2 Design
Persuasive Argument
Movement
of Head
Nodding
Shaking
Tuition decrease
Tuition increase
Tuition decreaseNodding
Tuition increaseNodding
Tuition decreaseShaking
Tuition increaseShaking
Main Effects
Effect each variable has by itself
DV: Willingness to accept increases in
tuition
Persuasive Argument
Head
Movement
Decrease
Increase
Nodding
400
630
Shaking
485
465
Main Effect for Head Movement
Persuasive Argument
Head
Movement
Increase
Decrease
Overall means
Nodding
400
630
515
Shaking
485
465
475
Main Effect for Type of Argument
Persuasive Argument
Head
Movement
Increase
Decrease
Nodding
400
630
Shaking
485
465
Overall means
442.5
547.5
Both Main Effects
Persuasive Argument
Head
Movement
Increase
Decrease
Overall
means
Nodding
400
630
515
Shaking
485
465
475
Overall means
442.5
547.5
Interactions
The effect of one independent variable
depends on the level of the other
There is an interaction in the persuasive
argument study

The effect of the type of argument is different
depending on whether the person is nodding or
shaking their head
Let’s take a closer look
Interactions
We can look at the data to detect the
interaction

YUCK!!
Persuasive
Argument
Head
Movement
Decrease
Increase
Nodding
400
630
Shaking
485
465
Interactions
Willing to accept increase
We can look at a line graph 
700
600
500
Nodding
400
Shaking
300
200
100
0
Decrease
Increase
Type of Question
Interactions
Willing to accept increase
Or we can look at a bar graph 
700
600
500
Nodding
400
Shaking
300
200
100
0
Decrease
Increase
Type of Question
Interactions
Ordinal (spreading) interaction

IV1 has an effect under one condition of IV2
but less of an effect under the other condition of
IV2.
Disordinal (crossover) interaction
There are no main effects of either IV
 The effects of each IV are opposite at different
levels of the other IV

Ordinal Interaction
Willing to accept increase
IV1 has an effect under one condition of IV2 but less of an
effect under the other condition of IV2.
700
600
500
Nodding
400
Shaking
300
200
100
0
Decrease
Increase
Type of Question
Another Ordinal Interaction
Percent Error
IV1 has an effect under one condition of IV2 but less of an
effect under the other condition of IV2.
45
40
35
30
25
20
15
10
5
0
Knowledgeable
Naïve
Unbiased
Misleading
Type of Question
Disordinal Interaction
There are no main effects of the IVs
 The effects of each IV are opposite at different
levels of the other IV
Percent Recall

45
40
35
30
25
20
15
10
5
0
Mood during LEARNING
Happy
Happy
Sad
Mood during RECALL
Sad
Concept Check
A professor randomly assigns students to one of four
conditions:




Learn words in the morning and drink 2 cups of coffee
Learn words in the afternoon and drink 2 cups of coffee
Learn words in the morning and drink no coffee
Learn words in the afternoon and drink no coffee
What are the main effects and the interactions in this
design?

What questions would you ask to evaluate these effects?
Concept Check
Main effect 1: Coffee factor

Are there any differences in students who received
coffee compared to those who didn’t?
Main effect 2: Time of day factor

Are there any differences in students who learned the
words in the morning vs afternoon?
Interaction: Does the effect of coffee depend on
the time of day?

Coffee might enhance performance in the morning but
impair performance in the afternoon.
Main Effects & Interactions
No main effect of A or B, no interaction
25
Violent TV
20
Threat
Provocations
A1
A2
B1
20
20
20
B2
20
20
20
20
20
15
B1
B2
10
5
-
0
A1
A2
Main effect of A, no main effect of B and
no interaction
Violent TV
Threat
-
A1
A2
B1
20
40
30
B2
20
40
30
20
40
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
Main effect of B, no main effect of A and
no interaction
Violent TV
Threat
-
A1
A2
B1
20
20
20
B2
40
40
40
30
30
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
Main effect of A and B, no interaction
Violent TV
Threat
-
A1
A2
B1
0
20
10
B2
20
40
30
10
30
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
No main effect of A or B; interaction
Violent TV
Threat
-
A1
A2
B1
40
20
30
B2
20
40
30
30
30
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
Main effect of A, no main effect of B;
interaction
Violent TV
Threat
A1
A2
B1
40
0
20
B2
20
20
20
30
10
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
Main effect of B, no main effect of A;
interaction
Violent TV
Threat
A1
A2
B1
20
0
10
B2
20
40
30
20
20
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
Main effect of A and B; interaction
Violent TV
Threat
-
A1
A2
B1
20
20
20
B2
20
40
30
20
30
45
40
35
30
25
20
15
10
5
0
Provocations
B1
B2
A1
A2
Hands on Activities
Design Identification
Outcomes of Factorial Designs