Methods of Control in Experimental Research Flashcards
3 factors that cause variability in a dependent variable:
- Independent variable (experimental variance)
- Systematic error (error due to ___________________)
- ________________ error (due to non-systematic fluctuations in subjects, conditions, methods of measurement, etc.)
- Extraneous variables
- Random error
An _____________________ variable is a source of systematic error, because it correlates with the dependent variable.
Extraneous (confounding).
Controlling Variability Due to Extraneous Variables - ____________________: Randomly assign subjects to different levels of the independent variable; this is the most powerful method of experimental control.
Random Assignment to Treatment Groups.
Controlling Variability Due to Extraneous Variables - ____________________: Select subjects who are homogenous with respect to the variable; this may limit the study’s generalizability.
Holding the Extraneous Variable Constant.
Controlling Variability Due to Extraneous Variables - ____________________: Match subjects in terms of their status on the EV and randomly assign matched subjects to one of the Tx groups.
Matching Subjects on the Extraneous Variable.
Controlling Variability Due to Extraneous Variables - ____________________: Include the EV as an additional IV so that its effects on the DV can be statistically analyzed. With this method, subjects are “blocked” (grouped) on the basis of their status on the EV, then subjects in each block are randomly assigned to a treatment group.
Building the Extraneous Variable into the Study (“Blocking”).
Controlling Variability Due to Extraneous Variables - ____________________: Use an ANCOVA or other statistical technique to remove variability in the DV that is due to the EV.
Statistical Control of the Extraneous Variable.
Conducting true experimental research allows investigators to minimize the effects of __________________ by controlling experimental conditions and procedures.
Random error.
