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Epidemiological research studies how an illness or characteristic is distributed across the population. Such studies can be helpful in planning treatment needs as well as suggesting possible causes for a problem.
Correlational methods measure the relationship between two (or more) variables (for example, between course grades and anxiety). They are widely used in abnormal psychology but, because they do not actually manipulate variables, it is difficult to draw conclusions about causation from them.
In experiments one (or more) independent variables are actually manipulated and the effects of the change on dependent variable( s) are studied. Experiments are preferred for studying causation. However, in abnormal psychology, many variables cannot be manipulated for practical or ethical reasons. Experiments seek internal validity by using procedures such as control groups and random assignment. External validity is difficult with any research design. The single-subject ABAB design studies the effect on a single individual's behavior of repeatedly (a) holding back and, (b) applying some manipulation. This design can produce dramatic effects although generalizability is difficult.
Mixed designs combine correlational and experimental techniques by actively manipulating only some variables.
ESSENTIAL CONCEPTS
1. Science is the pursuit of systematized knowledge through observation, although it is not purely objective and is influenced by the paradigms of the researcher and of society.
In order to be considered scientific, ideas must be publicly testable, and reliable or repeatable.
Scientific theories both account for data and generate hypotheses. Theoretical concepts bridge spatial and temporal relations and summarize observed relations.
The case study lacks control and objectivity, but it can be useful for (a) describing unusual phenomena, (b) disconfirming supposedly universal aspects of a theory, and (c) generating hypotheses.
Epidemiological research investigates the frequency and distribution of some problem or variable in the population. Such research is useful for social planning and can suggest causes of a problem.
Correlational methods study the degree of association between two or more variables (for example, IQ and grades). The variables are only observed, not manipulated. Thus, directionality and third-variable problems are difficult to answer and causal inferences are risky.
Statistical significance refers to a convention adopted by scientists wherein a finding is not considered to be meaningful unless the odds are less than 5 in 100 that it occurred by chance.
An experiment differs from a correlational method because one of the variables is actively manipulated. When properly conducted, an experiment is a powerful tool to study causality but ethical and practical problems often limit its use in studying psychopathology. 2. 3 . 4 . 5 . 6. 7 . 8.
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9. The basic features of an experiment include the experimental hypothesis, independent variables, dependent variables, and experimental effects.
Internal validity refers to whether the results obtained can be confidently attributed to the independent variable. Internal validity is aided by control groups and random assignment to eliminate confounds. There is debate over the role of placebo controls in psychological research.
11. External validity concerns generalizability of a particular study. It is difficult to evaluate. 12. Analogue experiments are frequently used to study psychopathology but their external
validity is always of concern.
Single-subject research can dramatically demonstrate a phenomenon in one subject although generalizability is a problem.
Mixed designs study the effect of several variables, some of which are observed (as in correlational methods) and some of which are actually manipulated (as in the experiment). 10. 13. 14.
KEY
TERMS Science (p. 106) Theory (p. 106) Case study (p. 109) Epidemiology (p. 11 1) Prevalence (p. 111) Incidence (p. 111) Risk factors (p. 111)Lifetime prevalence rates (p. 112)
Correlational method (p. 112) Correlation coefficient [r] (p. 113)
5 8 Chapter 5 Classificatory variables (p. 1 15) Directionality problem (p. 1 15) High-risk method (p. 115) Third-variable problem (p. 1 16) The experiment (p. 116) Experimental hypothesis (p. 1 17) Independent variable (p. 1 17) Random assignment (p. 117) Dependent variable (p. 117) Experimental effect (p. 1 17) Control group (p. 117) Confounds (p. 118) Internal validity (p. 118) Placebo effect (p. 118)
Placebo control group (p. 119)
Double-blind procedure (p. 119)
External validity (p. 120)
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Single-subject experimental design (p. 12 1)
Reversal [ABAB] design (p. 122)
Mixed design (p. 122)
Meta-analysis (p. 124)
STUDY QUESTIONS
SCIENCE AND SCIENTIFIC METHODS (p. 106-109)
1. Describe two basic requirements of any scientific approach. Identify two roles of theory. In constructing theories, what are two advantages of theoretically inferred concepts and two views on judging the legitimacy of theoretical concepts? (p. 106-109)
THE RESEARCH METHODS OF ABNORMAL PSYCHOLOGY (p. 109-123)
2. List six research methods of abnormal psychology (on pages 109 to 122). What is done in
a case study (the first method)? Describe three ways in which case studies are useful. (p.
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3 . What is epidemiology? Describe two uses of epidemiological research in psychopathology. (p. 111-112)
4 . What are correlational methods and how are they different from experimental research? How are correlations measured and their significance evaluated? (p. 112-1 14)
5 . Why are correlational methods often used in studying psychopathology? What is their major drawback and two reasons for it? (p. 114-1 16)
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How does the experiment overcome the drawback of correlational methods? Identify five basic features of the experimental design. How is the significance of an experimental effect
determined? (p. 1 16-1 17)
6 .
7. What is internal validity? Describe how control groups and random assignment are used to eliminate confounds and provide internal validity. (p. 1 17-1 18)
8 . In psychotherapy research, how are placebo effects viewed and controlled? Describe issues
in using placebo controls in psychotherapy research. What is external validity and why is it difficult to demonstrate? (p. 118-120)
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9. What are analogue experiments?
analogues in experimental designs? (p. 120-12 1)
What is an advantage and a disadvantage of using
10. What is the single-subject ABAB design and how does it show that the manipulation produced the result? What is the primary disadvantage of this design? (p. 121-122)
11. What is a mixed design? Give examples, explaining why they are mixed designs. Identify an advantage and a disadvantage of mixed designs. (p. 122-123)
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