Correlational Research
Inferential/Descriptive Statistic (r)
Describes strength of linear relation between two variables
Strength of relation = degree of association
Does knowing an individual’s score on A tell
you much about that individual’s score on
B? How much does it tell you?
Some properties of r
Ranges between -1 and 1 inclusive
Sign (+ or -) gives direction of relation
Absolute value gives strength
r2 gives proportion of variance accounted for
Correlations
140
130
120
110
100
90
Verbal IQ
80
70
60
60
70
80
90
100
110
120
Performance IQ
Correlation between VIQ and PIQ = +.53
Characterized as strong and positive
130
140
Correlations
8
7
6
consicentiousness
5
4
3
2
-6
-4
-2
0
2
4
6
8
underco, i/i, mr, teaimp, eysenck
Correlation between C and Behavioral Impulsivity = -.41
Characterized as moderate-strong and negative
Correlations
8
7
6
consicentiousness
5
4
3
2
0
10
20
30
40
50
family social class
Correlation between C and Family SES = -.15
Characterized as weak-negligible
60
Correlational Research
Disadvantages:
1) correlation does not indicate causation
2) problems with self-report method
Advantages:
1) can collect much information from many subjects at one time
2) can study a wide range of variables and their interrelations
3) study variables that are not easily produced in the laboratory
Correlational Research
Definition:
Seeks to establish a relation/association/correlation between two
or more variables that do not readily lend themselves to
experimental manipulation
Disadvantages:
1) correlation does not indicate causation
2) problems with self-report method
Advantages:
(6slide
causation example)
1) can collect much information from many subjects at one time
2) can study a wide range of variables and their interrelations
3) study variables that are not easily produced in the laboratory
Correlation is not Causation
Three ways in which A and B may be causally related
A causes B (either directly or indirectly)
A
B
B causes A (either directly or indirectly)
B
A
A third variable causes both A and B
A
C
B
Correlations Inform Causation
Causation implies Correlation
If A and B are causally related, they must be correlated
Design or theory informs direction of influence
Longitudinal design
Experimental design
Appeal to strong theory
Can model third variable effects
Specify and measure likely third variables
Control for third variables in model
If association between A and B remains,
then third variable explanation does not hold
Case In Point
Lynam, D.R., Moffitt, T.E., & Stouthamer-Loeber, M.A. (1993).
Explaining the relation between IQ and delinquency:
Class, race, test motivation, school achievement, or selfcontrol? Journal of Abnormal Psychology, 102, 187-196.
IQ is negatively correlated with delinquency
Think of some ways this relationship could work.
In other words, why or how might lower IQ be
related to delinquency?
What are other possibilities?
Delinquency leads to low IQ?
Third Variables?
What are the likely candidates?
Social Class
Race
Impulsivity
What happens when they are included?
Original r = -.25
Partial r = -.15
Significant relation remains
IQ Delinquency via School
Achievement?
What happens when school achievement is included?
Correlational Research
Definition:
Seeks to establish a relation/association/correlation between two
or more variables that do not readily lend themselves to
experimental manipulation
Disadvantages:
1) correlation does not indicate causation
2) problems with self-report method
Advantages:
1) can collect much information from many subjects at one time
2) can study a wide range of variables and their interrelations
3) study variables that are not easily produced in the laboratory
Correlational Research Example
Reformulated learned helplessness:
When people find they are helpless, they ask why
three dimensions of causal attributions
internal-external
specific-global
stable-unstable
internal, global, and stable attributions lead to
depression
Attributional Style Questionnaire
Should find correlation between I, S, G
attributional style and level of depression
Attributional Style Questionnaire
You have been looking unsuccessfully for a job for some time.
1. Write down one major cause.
2. Is the cause of your unsuccessful job search due to something about you,
or to, something about other people or circumstances ?
Totally due
Totally due
to others1
2
3
4
5
6
7 to me
3. In the future, when looking for a job, will this cause again be present?
Will never again
Will always
be present1
2
3
4
5
6
7be present
4. Is this cause something that influences just looking for a job, or does it
also influence other areas of your life?
Influences this
Influences all
situation 1
2
3
4
5
6
7situations
5. How important would this situation be if it happened to you?
Not at all
Extremely
important1
2
3
4
5
6
7important
Quasi-Experimental Research
Definition:
Blends correlational and experimental approaches. Typically
examines interaction between an individual difference variable and
an experimental manipulation
(expericorr example)
Disadvantages: similar to those of correlational research
1 Third variable problem still remains
Advantages: similar to those of correlational research
1 Can tease out cause and effect somewhat better if have
manipulated variable
Quasi-experimental Example
Discounting: Tendency to choose smaller,
immediately available rewards over larger,
delayed rewards
Hypothetical Money Choice Task
Choice is offered: smaller, immediately
available reward or larger delayed one
Chooses immediate reward, task is over and value
is recorded
Chooses delayed reward, new choice with larger
immediate reward is offered
Waiting for larger immediate reward
before switching shows less discounting
HMCT (Version 1)
You can have:
$5 now
or
$100 in 1 week
Which would you choose?
$5 now
$100 in 1 week
HMCT (Version 1)
You can have:
$10 now
or
$100 in 1 week
Which would you choose?
$10 now
$100 in 1 week
HMCT (Version 1)
You can have:
$15 now
or
$100 in 1 week
Which would you choose?
$15 now
and so on….
$100 in 1 week
HMCT (Version 2)
You can have:
$5 now
or
$100 in 1 month
Which would you choose?
$5 now
$100 in 1 month
HMCT (Version 2)
You can have:
$10 now
or
$100 in 1 month
Which would you choose?
$10 now
$100 in 1 month
Hypothetical Results
Effect of Condition:
Version 1
Version 2
$80.25
$70.25
Interaction of Condition and SS:
Version 1
Version 2
Low SS
$85.25
$65.25
High SS
$65.00
$65.00
Quasi-Experimental Research
Definition:
Blends correlational and experimental approaches. Typically
examines interaction between an individual difference variable and
an experimental manipulation
Disadvantages: similar to those of correlational research
1 Third variable problem still remains
Advantages: similar to those of correlational research
1 Can tease out cause and effect somewhat better if have
manipulated variable
Locus of Control Scale
For each pair of statements, choose the one with which you most agree:
1a. Many of the unhappy things in people's lives are due partly to bad luck.
1b. People's misfortunes result from the mistakes they make.
2a. One of the major reasons we have wars is that people don't take enough
interest in politics.
2b. There will always be wars, no matter how hard people try to prevent them.
3a. Sometimes I can't understand how teachers arrive at the grades they give.
3b. There is a direct connection between how hard I study and the grades I
get.
4a. The average citizen can have an influence in government decisions.
4b. This world is run by the few people in power and there isn't much the little
guy can do about it.
Scoring: Give yourself one point for each of the following: 1a, 2b, 3a, 4b
Quasi-Experimental Research
Locus of Control
Beliefs about one’s ability to influence outcomes
Similar to learned helplessness
Assessed with LOC scale
Selected participants to be high or low in external LOC
Randomly assigned participants to one of two conditions
Performance task with shock that is very easy to learn to avoid
Performance task with shock that is hard to learn to avoid
Findings in line with hypotheses
In easy task most people learned how to avoid shock
In harder task, Ps with high external LOC were less likely to learn
Problems to Look For
Experimental confound: when another variable is allowed
to vary with the independent variable.
Third variable problem
Nonrandom samples: when samples are selected so that
not everyone has an equal opportunity to participate.
Failure to replicate: single experiments do not constitute
facts.
Failure to include relevant comparison groups: lack an
adequate baseline or normative data.
(Example)
Failure to Include Comparison
Make people happy or sad and examine effects on
aggression:
Aggression
Sad
Happy
7.5
3.0
The meaning depends on a control group:
Sad
Control
Happy
1)
7.5
7.5
3.0
2)
7.5
5.0
3.0
3)
7.5
3.0
3.0