abnormal PSYCHOLOGY Third Canadian Edition Prepared by: Tracy Vaillancourt, Ph.D. Chapter 5 Research Methods in the Study of Abnormal Behaviour

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

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