Steps and Validity in Experimental Research: A Comprehensive Guide

1. Chapter 8 Experimental Research Conducting & Reading Research Baumgartner et al

2. Steps in Experimental Research • Stating the research problem • Determining if experimental approach is appropriate • Specifying the independent variable(s) • Specifying all potential dependent variables • Stating the tentative hypotheses • Determining availability of measures for potential dependent variables • Pausing to consider success potential of the research • Identifying full potential of intervening variables • Making a formal statement of the research hypotheses • Designing the experiment • Making final estimate of success potential of the study • Conducting the study as planned in steps 1 through 11 • Analyzing the data • Preparing a research report Conducting & Reading Research Baumgartner et al

3. Internal and External Validity • validity: How valid are the findings within the study? • validity: How much can the findings be inferred or generalized to other populations, settings, or treatments? • Must have good internal validity to have good external validity, but doesn’t guarantee good external validity. Conducting & Reading Research Baumgartner et al

4. Threats to Internal Validity • History • Maturation • Testing • Instrumentation • Statistical Regression • Selection • Experimental Mortality • Interaction of Selection and Maturation or History Conducting & Reading Research Baumgartner et al

5. Threats to External Validity • Interaction Effect of Testing • Interaction Effects of Selection Bias and Experimental Treatment • Reactive Effects of Experimental Setting • Multiple-Treatment Interference Conducting & Reading Research Baumgartner et al

6. Types of Designs • designs: variety of ways a research study may be structured or conducted Three main types of designs • experimental designs • experimental designs • designs Conducting & Reading Research Baumgartner et al

7. True experimental design • “ ” • random sampling of participants, random assignment to groups, all threats to internal validity controlled • Not always possible Conducting & Reading Research Baumgartner et al

8. Quasi-experimental design • “ ” • Lack either random sampling or random assignment • Controls threats to validity of history, maturation, testing, instrumentation, selection, and experimental mortality Conducting & Reading Research Baumgartner et al

9. Preexperimental designs • “ ” • no random sampling of participants, limited groups, control few threats to validity Conducting & Reading Research Baumgartner et al

10. Methods of Control • physical manipulation: researcher controls all aspects of participants’ environment and experience • selective manipulation • statistical techniques Conducting & Reading Research Baumgartner et al

11. Common Sources of Error • Hawthorne Effect: participants in an experiment may perform differently because they know they’re in a study • Placebo Effect: participants receiving treatment believe the treatment will have an effect (use single-blind approach) • “John Henry” Effect: Control group might try harder in attempt to outperform experimental group • Rating Effects: halo effect, overrater or underrater error, central tendency error • Experimental Bias Effect: try to control using double-blind approach • Participant-Researcher Interaction Effect: Gender issues, age, etc. • Post Hoc Error: Assuming cause-and-effect relationship where one does not exist Conducting & Reading Research Baumgartner et al