Chapter 9

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 effects occurring when the initial measurement or test alerts or primes subjects in a way that affects their response to the experimental treatments.

Instrumentation effects

A nuisance that occurs when a change in the wording of questions, a change in interviewers, or change in other procedure causes a change in the dependent variable.

Manipulation check

A validity test of an experiment to make sure that the manipulation does produce differences in the independent variable.

External validity

Accuracy with which experimental results can be generalized beyond the experimental subjects

Confound

An experimental confound means that there is an alternative explanation beyond the experimental variables for any observed differences in the dependent variable

Blocking variable

Categorical variable included in the statistical analysis of experimental data as a way of accounting for variance due to that variable

Systematic or nonsampling error

Occurs if the sampling units in an experimental cell are some-how 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

Mortality effects( sample attrition)

Occurs when some subjects withdraw from the experiment before its 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 experiment

Research project involving experimental manipulation that are implemented in a natural environment

Laboratory experiment

Research project involving experimental manipulation that are implemented in a natural environment in an artificial environment.

Placebo effects

The effects in a dependent variable associated with the psychological impact that goes along with knowledge of some treatment being administered

Main effects

The experimental difference in dependent variable between the difference levels of any single experimental variable

Internal validity

The extent to which experimental variable is truly responsible for any variance in the dependent variable

Randomization

The random assignment of subject and treatment to groups

Subjects

The sampling units for an experiment, usually human participants in research who are subjected to some experimental manipulation.

Test units

The subjects or entries whose responses to the experimental treatment are measured or observed

Experimental treatment

The term referring to the way an experimental variable is manipulated

Within-subject design

involves repeated measures because with each treatment the same subject is measured

demand effects

occurs when demand characteristics actually affect the dependent variable

Interaction effect

Difference in dependent variable means due to a specific combination of independent variable

Between-subject design

Each subject receives only one treatment combination

demand characteristics

Experimental design element or procedure that unintentionally provides subjects with hints about the research hypothesis

Repeated measures

Experiments in which an individual subjects is exposed to more than one level of an experimental treatment