Ch. 10: The Nonexperimental and Quasi-Experimental Strategies: Nonequivalent Group, Pre-Post, and Developmental Designs

Nonexperimental strategy

A research strategy that attempts to demonstrate a relationship between two variables by comparing different groups of scores, but makes no attempt to minimize threats to internal validity or to explain the relationship

Quasi-experimental research strategy

A research strategy that attempts to limit threats to internal validity and produce cause-and-effect conclusions (like an experiment), but lacks one of the critical components—either manipulation or control—that is necessary for a true experiment. Typically compares groups or conditions that are defined with a nonmanipulated variable

Nonequivalent group designs

A research study in which the different groups of participants are formed under circumstances that do not permit the researcher to control the assignment of individuals to groups and the groups of participants are, therefore, considered nonequivalent

Differential research design

A nonexperimental research design that compares preexisting groups rather than randomly assigning individuals to groups. Usually, the groups are defined by a participant characteristic such as gender, race, or personality

Nonequivalent control group design

A research design in which the researcher does not randomly assign individuals to groups but rather uses preexisting groups, with one group serving in the treatment condition and another group serving in the control condition

Posttest-only nonequivalnet control group design

A nonexperimental design in which one group is observed (measured) after receiving a treatment, and a second, nonequivalent group is measured at the same time but receives no treatment

Pretest-posttest nonequivalent control group design

A quasi-experimental research design comparing two nonequivalent groups; one group is measured twice, once before treatment is administered and once after. The other group is measured at the same two times but receives no treatment

Pre-post design

Quasi-experimental and nonexperimental designs consisting of a series of observations made over time. The goal is to evaluate the effect of an intervening treatment or event by comparing observations made before versus after the treatment

Pretest-posttest design

A nonexperimental design involving one measurement before treatment and one measurement after treatment for a single group of participants

Time-series design

A quasi-experimental research design consisting of a series of observations before a treatment or event and a series of observations after the treatment or event. A treatment is a manipulation administered by the researcher and an event is an outside occurrence that is not controlled or manipulated by the researcher

Developmental research designs

Nonexperimental research designs used to examine the relationship between age and other variables

Cross-sectional developmental research design

A developmental design comparing different groups of individuals, each group representing a different age

Cohorts

Individuals who were born at roughly the same time and grew up under similar circumstances

Cohort effects, or generation effects

Differneces between age groups that are caused by characteristics or experieces other than age. Also called generation effect

Longitudinal developmental research design

A developmental research design that examines development by making a series of observations or measurements over time. Typically, a group of individuals who are all the same age is measured at different points in time

Quasi-independent variable

In a quasi-experimental or nonexperimental research study, the variable that differentiates the groups or conditions being compared. Similar to the independent varaible in an experiment