abnormal
PSYCHOLOGY
Third Canadian Edition
Chapter 5
Research Methods in the Study
of Abnormal Behaviour
Prepared by:
Tracy Vaillancourt, Ph.D.
Science and Scientific Methods
• Science— pursuit of systematized
knowledge through observation
• Testability and replicability
• Theory—set of propositions meant to
explain a class of phenomena
– primary goal of science is to advance theories
• Hypotheses—expectations about what
should occur if a theory is true
Research Methods
1. Case Study
2. Epidemiological Research
• Epidemiology– study of frequency and distribution of a
disorder in a population
– Data are gathered about the rates of a disorder and its possible
correlates in a large sample or population.
• Focuses on determining 3 features of a disorder:
– 1. prevalence— proportion of a population that has the disorder
at a given point or period of time
– 2. incidence— # of new cases of the disorder that occur in some
period, usually a year
– 3. risk factors— conditions or variables that, if present, increases
the likelihood of developing the disorder
Research Methods cont.
3. Correlational Method
• Is there a relationship
between or among 2 or >
variables?
Measuring Correlation
• correlation coefficient (r)
– may take any value between 1.00
and 1.00
– measures magnitude and
direction of relationship
Statistical Significance
• likelihood results of an
investigation are due to chance
Problems of Causality
• Critical drawback of correlational research
– does not allow determination of cause-effect relationships
– correlation between two variables tells us only that they are
related or tend to co-vary with each
• Directionality problem
– how can we tell which is the cause and which is the effect?
– “correlation does not imply causation”
• High-risk method
• Third-variable problem
Experimental Design
• Generally considered most powerful tool for determining
causal relationships between events
– involves random assignment of participants to different
conditions
• involves manipulation of IV and measurement of DV
• Basic Features of Experimental Design
– 1. researcher typically begins with an experimental hypothesis
– 2. investigator chooses an independent variable that can be
manipulated
– 3. participants are assigned to the two conditions by random
assignment
– 4. researcher arranges for the measurement of a dependent
variable
– 5. produces an experimental effect
Experimental Design cont.
• Internal validity
– extent to which effect can be confidently attributed to
manipulation of IV
– important feature is inclusion of at least one control group that
does not receive the experimental treatment
• Confounders
• Placebo Effect
– placebo control group
– double-blind procedures
• External validity
– extent to which results can be generalized beyond immediate
study
Other Experimental Designs
• Single-subject experimental designs
– participants are studied one at a time and
experience a manipulated variable
• Reversal design or ABAB design
• Mixed design
Summary
Copyright
Copyright © 2008 John Wiley & Sons Canada, Ltd. All rights
reserved. Reproduction or translation of this work beyond that
permitted by Access Copyright (The Canadian Copyright
Licensing Agency) is unlawful. Requests for further information
should be addressed to the Permissions Department, John
Wiley & Sons Canada, Ltd. The purchaser may make back-up
copies for his or her own use only and not for distribution or
resale. The author and the publisher assume no responsibility
for errors, omissions, or damages caused by the use of these
programs or from the use of the information contained herein.