Slide 1
2
Research Methods
In Psychology
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Research Methods In Psychology
Basic Concepts of Research
• Basis of scientific method
– Making observations in systematic way
– Follow strict rules of evidence
– Critical thinking about evidence
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 2
Research Methods In Psychology
Empirical Evidence and Operational
Definitions
• Empirical evidence – observations of
publicly (confirmable) observable behavior
• Operational definitions – use operations
of measurement to describe observations
– Evaluates quality of evidence and allows
alternative interpretations
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 3
Research Methods In Psychology
Theories and Hypotheses
• Theories – tentative explanations of facts
and relationships in science
• Hypothesis – a prediction based on a theory
– Tested to confirm or refute
– Can be revised or abandoned
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 4
Research Methods In Psychology
Representativeness of Samples
• Sample
– Representative of larger group or population of
interest
– Small group of humans or animals
– Unrepresentative sample – misleading or biased
test of hypothesis
• Replication of research removes most doubt
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 5
Research Methods In Psychology
Research Methods
• Descriptive studies
– Simplest method of scientific inquiry
– Describe behavior and mental processes
– Most widely used
• Survey method – ask people’s opinions
• Naturalistic observation – watch, describe
• Clinical method – observe in clinic setting
– All have advantages and disadvantages
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 6
Research Methods In Psychology
Research Methods
• Correlational Studies
– Correlational method: measure two
variables for statistical relationship
– Variable: anything that can be assigned a
numerical value
– Uses quantitative measures
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 7
Research Methods In Psychology
Research Methods
• Correlational Studies
– Correlation coefficient
• Measures each variable
• Indicates strength ( 0 to 1) and direction
(negative or positive) of relationship
– Correlation does not mean causation
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Slide 9
Fig. 2.2
30
29
28
Hypothetical
data illustrating
a correlation
coefficient of
+1.00
Variable 2
27
26
25
24
23
22
21
20
1
2
3
4
5 6 7
Variable 1
8
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
9
10
Slide 10
Fig. 2.3
30
29
28
Hypothetical
data illustrating
a correlation
coefficient of
-1.00
Variable 2
27
26
25
24
23
22
21
20
1
2
3
4
5 6 7
Variable 1
8
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
9
10
Slide 11
Fig. 2.4
30
29
28
Hypothetical
data illustrating
a correlation
coefficient of
zero
Variable 2
27
26
25
24
23
22
21
20
1
2
3
4
5 6 7
Variable 1
8
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
9
10
Research Methods In Psychology
Slide 12
Formal Experiments
• Tests relationship of two or more variables
– Allows conclusions about cause-and-effect
– Quantitative measures of behavior compared in
different conditions created by researchers
– Evidence supports or rejects hypothesis
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Research Methods In Psychology
Slide 13
Formal Experiments
• Elements
– Independent variable – gets manipulated
– Dependent variable – amount of change
– Experimental group – exposed to independent
variable or conditions expected to create change
– Control group – presents normal behavior
used for comparison
– Random assignment
–
– Experimental control
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 14
Fig. 2.6
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
Nonviolent Violent film
film
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 15
Fig. 2.7
Full population of interest
Randomly
assign into
control and
experimental
groups
Experimental group:
exposed to independent
variable: view violent film
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Control group:
View nonviolent film
Research Methods In Psychology
Formal Experiments
• Placebo control
– Placebo effect: provides no active effect
– Use in identical conditions for control and
experimental groups
• Blind experiment
– Researchers blind to group membership of
participants to rule out experimenter bias
• Strongest experiments – double blind
– Researchers and participants kept blind
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 16
Research Methods In Psychology
Slide 17
Describing and Interpreting Data
• Descriptive statistics – summarized data for
large groups of participants
– Mean: average
– Median: midpoint in rank-ordered data
– Mode: score appearing most often
– Normal distribution: bell-shaped curve
– Standard deviation: degree to which scores in
ordered distribution are spread out
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 18
Mode
9
Mean & Median
% Giving birth for 1st time
8
7
6
5
4
3
2
1
0
13
16
19
22
25
28
Mother’s Age
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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37
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Research Methods In Psychology
Describing and Interpreting Data
• Reaching conclusions from data
– Statistical significance
• Size of correlation
• Difference of means are greater than chance
– Two issues for significance
• Larger sample size is better
• Statistical difference does not equal practical
significance
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 19
Research Methods In Psychology
Ethical Principles of Research
• Ethics in research with human participants
– Freedom from coercion
– Informed consent
– Limited deception
– Adequate debriefing
– Confidentiality
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 20
Research Methods In Psychology
Ethical Principles of Research
• Ethics of research with nonhuman animals
– Necessity
– Health
– Humane treatment
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 21
Research Methods In Psychology
Human Diversity: Equal
Representation in Research
• U.S. National Institutes of Health
– New applications for research grants
involving human subjects must include
diverse samples of
• Both sexes
• Major racial and cultural groups
– Differences may be real and important
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Research Methods In Psychology
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The End
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved