abnormal PSYCHOLOGY

Fourth Canadian Edition

Chapter 5Chapter 5Research Methods in the Study

of Abnormal BehaviourPrepared by:

Tracy Vaillancourt, Ph.D.

Modified by: Réjeanne Dupuis, M.A.

Chapter OutlineA. Science and Scientific Method

I. Testability and Replicability II. The Role of Theory

B. Research MethodsI. The Case StudyII. Epidemiological Research III. The Correlational Method IV. The Experiment V. Single-Subject Experimental Research VI. Mixed DesignsVII. Meta-analysis

A. Science and Scientific Methods

• Science: The pursuit of systematized knowledge through observation

I. Testability and Replicabilitya. A hypothesis must be amenable to systematic testing

that could show it to be false b. Hypothesis: Expectations about what should occur if a

theory is trueII.The Role of Theory

a. Primary goal of science is to advance theoriesb. Theory: A set of propositions meant to explain a class

of phenomena

B. Research MethodsI. Case Study• The detailed study of one individual, based on a paradigm

• Providing detailed descriptions − Collecting historical and biographical information − Often includes details of therapy sessions − Several case studies can be compared and analyzed for

common elements through a specific method

• The case study as evidence − Particularly useful to negate a universal theory or law − Not useful to rule out alternative hypotheses

• Generating hypothesis− Exposure to a large number of cases may allow the clinician to

notice similarities of circumstances and outcomes

B. Research MethodsII. 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– Provides a general picture of a disorder

• 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 time2. Incidence: # of new cases of the disorder that occur in some

period, usually a year3. Risk factors: Conditions or variables that, if present, increases

the likelihood of developing the disorder

B. Research Methods (cont.)

III. Correlational Method• Is there a relationship between or

among 2 or more 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 Applications to Psychopathology

B. Research Methods (cont.)

III. Correlational Method cont.

• 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– Prospective, longitudinal design helps resolve the directionality

issue – High-risk method: individuals with a predisposition are studied

• Third-variable problem

B. Research Methods (cont.)

IV. Experimental Design

• Generally considered most powerful tool for determining causal relationships between events– Involves (1) random assignment of participants to different

conditions (2) manipulation of IV and measurement of DV

• Basic Features of Experimental Design1. Researcher typically begins with an experimental hypothesis2. Investigator chooses an independent variable (IV) that can be

manipulated3. Participants are assigned to the two conditions by random

assignment 4. Researcher arranges for the measurement of a dependent variable

(DV)5. Produces an experimental effect

B. Research Methods (cont.)

IV. Experimental Design cont.

• Internal validity– Extent to which effect can be confidently attributed to

manipulation of IV; Inclusion of at least one control group• Confounders• Placebo Effect

– Placebo control group; Double-blind procedures• External validity

• Can the results be generalized beyond immediate study?• Analogue experiments

– The use of a related phenomenon (an analogue) in the lab • Randomized Controlled Trials (RTC)

B. Research Methods (cont.)

V. Single-Subject Experimental Designs• Participants are studied one at a time and experience a

manipulated variable

– Reversal design or ABAB design Measurement of a specific behaviour at different times:(1) During an initial time period, the baseline (A)(2) During a period when treatment is introduced (B)(3) During a reinstatement of the condition that prevailed in the

baseline period (A) (4) During the re-introduction of the experimental manipulation

(B)

B. Research Methods (cont.)

VI. Mixed Designs• The combination of experimental and correlational

designs

• Classificatory or correlational variables (e.g., having PTSD or not) are not manipulated nor created by the researcher

• Experiments demand the manipulation of a variable (e.g., 3 types of treatment for major depression)

B. Research Methods (cont.)

VII. Meta-Analysis • The review of several studies in order to determine the

effects of treatment, using a statistic called effect size

• Meta-analysis can hardly provide definite answers b/c:1. It is a complicated process that requires decisions at each of

numerous phases or steps 2. Results of a meta-analysis are difficult to interpret

• Despite difficulties and shortcomings, meta-analyses have been useful

Summary

Copyright

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