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Chapter 10: Experimental Research - Coggle Diagram
Chapter 10: Experimental Research
Basic Concepts
Treatment group: subjects are administered on or more experimental stimulus.
Control group: subjects are not given such a stimulus.
Treatment manipulation: the unique feature of experimental research that set this design apart from all other research methods.
Pretest measures: measurements conducted before the treatment is administered.
Posttest measures: measurements conducted after the treatment administered.
Random selection and assignment: the process of randomly drawing a sample from a population or a sampling frame.
Threats to internal validity
History threat: possibility that the observed effects caused by extraneous or historical events.
Maturation threat: the possibility that observed effects caused by natural maturation of subjects.
Testing threat: a threat in pre-post design where subjects' posttest responses are conditioned by their pretest responses.
Instrumentation threat: the possibility that the difference between pretest and posttest scores.
Mortality threat: possibility that subjects may drop out of a study at differential rates between the treatment and control groups.
Regression threat: the statistically tendency of a group's overall performance on a measure during a posttest to regress toward the mean of that measure rather than in the anticipated direction.
Two-Group Experimental Designs
Pretest-posttest control group design: subjects are randomly assigned to treatment and control groups, subjected to an initial measurement of the dependent variables of interest, the treatment group is administered a treatment and the dependent variables measured again.
Posttest-only control group design: simpler version of pretest-posttest design, pretest measurements are omitted.
Covariance designs: variables may be influenced by extraneous variables called covariates. Covariates are those variables that are not of central interest to an experimental study.
Factorial Designs
Main effect: exist if the dependent variable shows a significant difference between multiple levels of one factor, at all levels of other factors.
Interaction effect: exists when the effect of differences in one factor depends upon the level of a second factor.
Hybrid Experimental Design
Randomized block design: variation of posttest-only or pretest-posttest control group design where the subject population can be grouped into relatively homogenous subgroups within which the experiment is replicated.
Solomon four-group design: the sample is divided into two treatment groups and tow control groups.
Switched replication design: implemented in two phases with three waves of measurement.
Quasi-Experimental Designs: almost identical to true experimental designs, but lacking one key ingredient: random assignment.
Nonequivalent groups design: quasi-equivalent version of pretest-posttest control group design.
Non-equivalent switched replication design: quasi-experimental version of switched replication design.
Proxy pretest design: the pretest score is collected after the treatment is administered.
Nonequivalent dependent variable design: single-group pre-post quasi-experimental design with two outcome measures, one measure is theoretically expected to be influenced by the treatment and the other measure is not.
Perils of Experimental Research
Experimental research is one of the most difficult of research designs, and should not be taken lightly.
Many of the measurement instruments used in experimental research are not tested for reliability and validity, and are incomparable across studies.
Experimental research use inappropriate research designs, such as irrelevant dependent variables, no interaction, no experimental controls, and non-equivalent stimulus across treatment groups.
Treatments used in experimental research may be diverse, incomparable, and inconsistent across studies and sometimes inappropriate for the the subject population.
Experimental Research: one or more independent variables are manipulated by the researcher, subjects are randomly assigned to different treatment levels and the results of the treatments on outcomes are observed.
Laboratory experiments: conducted in a laboratory settings and tend to be high in internal validity.
External validity: the study is conducted may not reflect the real world.
Field experiments: conducted in field settings such as in a real organization, and high in both internal and external validity.