| III. Research that
Describes, Predicts, & Explains Behavior (i.e., cause and effect)
The True Experiment: A research method in which an
investigator manipulates one or more factors (independent variables)
in order to observe the effect on some behavior or mental process (dependent
variable). By randomly assigning participants to
groups, other relevant factors are controlled.
Independent Variable: The factor that is being
manipulated by the researchers. The theoretical "cause" in the
cause and effect relationship.
Dependent Variable: The factor (a behavior or
mental process) that is being measured by the researchers. The
variable that is predicted to change in response to the manipulation of
the IV.
Operational Definitions: Specific statements
describing how the the IV is manipulated and how the DV is measured.
Random Assignment: Assigning participants to
control and experimental conditions on the basis of chance, thus
minimizing pre-existing differences between the groups (i.e., it
controls preexisting subject variables.
Experimental Condition (or Group): The condition
of an experiment that exposes participants to the treatment of interest,
that is, to one level of the independent variable.
Control Condition (or Group): The condition of
an experiment that contrasts with the experimental condition and serves
as a comparison for evaluating the effect of the treatment.
*At the conclusion of an experiment, the mean scores the experimental
and control groups receive on the DEPENDENT VARIABLE are COMPARED to
determine if a statistically significant difference exists.
Internal Validity: The extent to which one can be confident
that the manipulation of the IV caused the changes in the DV.
Internal validity can be assured only if all potential confounding
variables have been controlled. |
Control Techniques used
to control confounding variables.
Random Assignment: Controls pre-existing subject variables.
Control Group: Controls history, maturation, and
testing effects.
Placebo: An inert substance given to the control
group in place of an actual medication. It controls the Placebo
Effect.
Placebo Effect: Experimental results caused by the subjects'
expectations alone.
Double-Blind Design: An experimental procedure
in which both the research participants and the research staff are
ignorant (blind) about whether subjects are in the control or
experimental groups (commonly used in drug-evaluation studies).
This type of design controls subject and experimenter effects.
Subject Effects or Biases: Any response by subjects in a
study that does not represent how they would normally behave if not
under study. Two powerful subject effects are the placebo effect
and the demand characteristics of the study.
Demand Characteristics: Aspects of the study that suggest
to the subjects what type of behavior is expected or desired by the
researchers.
Experimenter Effects or Biases: Any behavior of a
researcher that might affect the behavior of the subjects or affect the
measurement and recording of the dependent variable.
The Quasi-experimental Design: Designs similar to true
experiments, but without all of the control techniques built in (e.g.,
random assignment may not be used).
See HANDOUTS for more information on research methods.
Ethics: The APA has strict guidelines which must be followed
when using both human and animal subjects. See
HANDOUT |