Chapter 9
Confound
An experimental confound means that there is an alternative explanation beyond the experimental variables for any observed differences in the dependent variable.
Counterbalancing
Attempts to eliminate the confounding effects of order of presentation by requiring that one-fourth of the subjects be exposed to treatment A first, one-fourth to treatment B first, one-fourth to treatment C first, and finally one-fourth to treatment D first.
Blocking Variables
Categorical variables included in the statistical analysis of experimental data as a way of statistically controlling or accounting for variance due to that variable.
Tachistoscope
Device that controls the amount of time a subject is exposed to a visual image.
Interaction Effect
Differences in dependent variable means due to a specific combination of independent variables.
Between-Subjects Design
Each subject receives only one treatment combination.
Internal Validity
Exists to the extent that an experimental variable is truly responsible for any variance in the dependent variable.
Demand Characteristic
Experimental design element or procedure that unintentionally provides subjects with hints about the research hypothesis.
Repeated Measures
Experiments in which an individual subject is exposed to more than one level of an experiment treatment.
Test-Market Sabotage
Intentional attempts to disrupt the results of a test market being conducted by another firm.
Within-Subjects Design
Involves repeated measures because with each treatment the same subject is measured.
External Validity
Is the accuracy with which experimental results can be generalized beyond the experimental subjects.
Constancy of Conditions
Means that subjects in all experimental groups are exposed to identical conditions except for the differing experimental treatments.
Systematic or Nonsampling Error
Occurs if the sampling units in an experimental cell are somehow different than the units in another cell, and this difference affects the dependent variable.
History Effect
Occurs when a change other than the experimental treatment occurs during the course of an experiment that affects the dependent variable.
Demand Effect
Occurs when demand characteristics actually affect the dependent variable.
Mortality Effect (Sample Attrition)
Occurs when some subjects withdraw from the experiment before it is completed.
Experimental Condition
One of the possible levels of an experimental variable manipulation.
Cohort Effect
Refers to a change in the dependent variable that occurs because members of one experimental group experienced different historical situations than members of other experimental groups.
Cell
Refers to a specific treatment combination associated with an experimental group.
Field Experiments
Research projects involving experimental manipulations that are implemented in a natural environment.
Covariate
A continuous variable included in the statistical analysis as a way of statistically controlling for variance due to that variable.
Maturation Effect
A function of time and the naturally occurring events that coincide with growth and experience.
Experimental Group
A group of subjects to whom an experimental treatment is administered.
Control Group
A group of subjects to whom no experimental treatment is administered.
Testing Effects
A nuisance effect occurring when the initial measurement or test alerts or primes subjects in a way that affects their response to the experimental treatments.
Instrumentation Effect
A nuisance that occurs when a change in the wording of questions, a change in interviewers, or a change in other procedures causes a change in the dependent variable.
Manipulation Check
A validity test of an experimental manipulation to make sure that the manipulation does produce differences in the independent variable.
Placebo Effect
The effect in a dependent variable associated with the psychological impact that goes along with knowledge of some treatment being administered.
Main Effect
The experimental difference in dependent variable means between the different levels of any single experimental variable.
Randomization
The random assignment of subject and treatments to groups; it is one device for equally distributing the effects of extraneous variables to all conditions.
Laboratory Experiment
The researcher has more complete control over the research setting and extraneous variables.
Subjects
The sampling units for an experiment, usually human participants in research who are subjected to some experimental manipulation.
Test Units
The subjects or entities whose responses to the experimental treatment are measured or observed.
Experiment Treatment
The term referring to the way an experimental variable is manipulated.