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Slide 1

Research Methods In Psychology

2

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 2

Basic Concepts of Research

• Basis of scientific method– Making observations in systematic way

– Follow strict rules of evidence

– Critical thinking about evidence

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 3

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 4

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 5

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 6

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 7

Research Methods

• Correlational Studies

– Correlational method: measure two variables for statistical relationship

– Variable: anything that can be assigned a numerical value

– Uses quantitative measures

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 8

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 9

Fig. 2.2V

aria

ble

2

21

Variable 1

22

23

24

25

26

27

28

29

30

220

3 4 5 6 7 8 9 101

Hypothetical data illustrating

a correlation coefficient of

+1.00

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Slide 10

Fig. 2.3

Hypothetical data illustrating

a correlation coefficient of

-1.00

Var

iabl

e 2

21

Variable 1

22

23

24

25

26

27

28

29

30

220

3 4 5 6 7 8 9 101

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 11

Fig. 2.4

Hypothetical data illustrating

a correlation coefficient of

zero

Var

iabl

e 2

21

Variable 1

22

23

24

25

26

27

28

29

30

220

3 4 5 6 7 8 9 101

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

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

Research Methods In Psychology

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Slide 14

0.02

Nonviolent film

Violent film

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.00

Fig. 2.6

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 15

Fig. 2.7

Control group: View nonviolent film

Randomly assign into control and

experimental groups

Full population of interest

Experimental group: exposed to independent variable: view violent film

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 16

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 18

1

2

3

4

5

6

7

8

9

400

13 16 19 22 25 28 31 34 37

% G

ivin

g bi

rth

for

1st t

ime

Mother’s Age

ModeMean & Median

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Slide 19

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 20

Ethical Principles of Research

• Ethics in research with human participants

– Freedom from coercion

– Informed consent

– Limited deception

– Adequate debriefing

– Confidentiality

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 21

Ethical Principles of Research

• Ethics of research with nonhuman animals

– Necessity

– Health

– Humane treatment

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 22

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

Research Methods In Psychology

© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved

Slide 23

The End

2Research Methods In Psychology