RESEARCH STRATEGY
A general approach to
research determined by the kind of question that the research study hopes to
answer.
A general plan for
implementing the research strategy. It
requires decisions about the following aspects of the research study.
An exact, step-by-step
description of a specific research study.
GOALS OF PSYCHOLOGICAL SCIENCE
To develop theories that
Describe (through the use of Observational or Descriptive Research)
Predict (through the use of Correlational Research)
Explain (through the use of Experimental Research)
Experimental procedures allow us to determine the causes of behavior.
THE EXPERIMENTAL METHOD
· An independent variable (IV) is manipulated. Conditions a re established by the experimenter.
· A dependent variable (DV) is measured.
· There are at least two levels (values) of the IV. In the simplest case, there is an experimental and a control group. The conditions associated with the different levels of an IV are called treatments.
Participants are assigned to the different levels and exposed to specific treatments. Then, the performance of individuals in the different treatment groups is compared.
· Extraneous variables are controlled through either experimental control (keeping variables constant) or randomization.
· Because the IV is directly manipulated and extraneous variables are controlled, a causal relationship between the IVs and DVs can be determined.
In a quasi-experimental study, a nonmanipulated or noncontrolled variable is used in place of the IV. Such studies cannot demonstrate cause-effect relationships.
One of the goals of research is to control extraneous variables in order to detect the effects of the IV.
INTERNAL VALIDITY
The extent to which we can accurately state that the IV produced the observed changes in the DV. If another explanation for the results exists, then the study lacks internal validity.
EXTRANEOUS VARIABLE
Any variable other than the IV that may influence the DV.
CONFOUND
An extraneous variable that systematically varies with changes in the IV.
Confounding is problematic because it affects internal validity.
CONSTANCY
Stability in the influence exerted by an extraneous variable in all treatment conditions.
We achieve control in a study if we can arrange extraneous variables in such a way that they have no differential influence on the results of the experiment.
EXTRANEOUS VARIABLES TO BE CONTROLLED
Participant-related:
SELECTION: The choice of participants to the various treatment groups on the basis of different criteria. (This creates assignment bias problems)
MATURATION: Changes in biological and psychological conditions of the individual that occur with the passage of time.
MORTALITY: A differential loss of participants from the various experimental groups. This is problematic because such a loss may produce differences in the groups that cannot be attributed to the experimental treatment.
Environment-related
HISTORY: Specific events that occur between the first and second measurement of the DV.
Measurement-related
INSTRUMENTATION: Changes that occur over time in the measurement of the DV.
STATISTICAL REGRESSION: The lowering of extremely high scores or the raising of extremely low scores during posttesting.
Practice effects (noticed with repeated measures)