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RESEARCH DESIGNS

RESEARCH DESIGNS. OVERVIEW. EXPERIMENTAL DESIGNS. When the Research Question Deals “with what happens if”. pretest data cannot be collected postest only design. pretest data can be collected pretest-postest design. Experimental Designs-random assignment. pretest data cannot be collected

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RESEARCH DESIGNS

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  1. RESEARCH DESIGNS OVERVIEW

  2. EXPERIMENTAL DESIGNS

  3. When the Research Question Deals “with what happens if”

  4. pretest data cannot be collected postest only design pretest data can be collected pretest-postest design Experimental Designs-random assignment

  5. pretest data cannot be collected postest only design pretest data can be collected pretest-postest design QUASIEXPERIMENTAL DESIGNno random assignment to groups

  6. Causality • TEMPORAL SEQUENCE • CONCOMITANT VARIATION • ABSENCE OF COMPETING EXPLANATIONS

  7. EXPERIMENTATION • RANDOMIZATION • CONTROL • MANIPULATION

  8. LOGIC OF A TRUE EXPERIMENT • When one starts a study with two groups who are equal with respect to important variables, administers a treatment to one group (experimental group) and not to the other (control group) holding all other conditions constant, any differences in the dependent variable following treatment probably were the result of that treatment.

  9. Experimental Designs O=measurement of dep. variable X=application of indep. variable R=randomization

  10. Pretest-postest experiment R O X O R O O

  11. Solomon Four group R O X O R O O R X O R O

  12. Postest Only R X O R O

  13. Repeated Measures R OOOO X OOOO R OOOO OOOO

  14. FACTORIAL DESIGN experimental if random assignment to cell

  15. Advantages of Experiments • -test cause and effect • -control threats to internal validity

  16. Disadvantages of Experiments • -assumes all of the relevant variables have been identified • -some variables not manipulable • -randomization may pose difficulties in field studies • -Hawthorne effect may not be avoidable

  17. quasiexperimental designs • lack either randomization and or a control group. (always have manipulation)

  18. Nonequivalent control group O X O O O

  19. Postest only-nonequivalent control group X O O

  20. Time Series-non equivalent groups OOOO X OOOO OOOO OOOO

  21. Time series design OOOO X OOOO

  22. Crossover design OO X OO X OO OO

  23. Advantages of Quasi-Experiments • -practical, feasible,generalizable • -adaptable to field studies • -for some hypotheses they may be the only way to test • -may save some experiments that suffer from attrition

  24. Disadvantages • -less confidence in causality • -need a priori controls • -must rule out alternative explanations • -need more replication

  25. EVALUATION RESEARCH

  26. objectives: • --to discover whether and how well objectives are being fulfilled • --to discover the reasons for specific successes and failures • --to direct the cours of experiment with techniques for increasing effectiveness • --to uncover principles underlying a successful program • --to redefine goals and objectives and means of obtaining them

  27. Nonexperimental designs

  28. DESCRIPTIVE/EXPLORATORY SURVEY • collect detailed data on the status quo • determine differences between varibles

  29. Descriptive/Survey Research • CHARACTERISTICS • ATTITUDES • FACTS • OPINIONS • BELIEFS • BEHAVIORS

  30. Descriptive Surveys • Use: questionnaires or interviews • Large samples • Superficial information emphasizes breadth rather than depth. • Researcher needs knowledge of techniques. • Can be costly.

  31. Descriptive Correlational Studies • Tests covariance between variables

  32. advantages • increased flexibility when investigating complex relationships among variables • efficient and effective method of collecting a large amount of data about a problem • potential for practical application in clinical settings • foundation for future experimental research studies • explores relationships between variables that are inherently not manipulable

  33. Disadvantages: • the researcher is unable to manipulate the variables • generalizability is decreased (preexisting groups) • no causal relationship

  34. EX POST FACTO DESIGNS “natural experiment” • independent variable not manipulated

  35. Types of Ex Post Facto Studies prospective retrospective longitudinal cross-sectional

  36. advantages: • similar to correlational advantages • realistic and natural

  37. disadvantages: • no causality • must rule out alternative explanations • finding similar comparison groups difficult

  38. Methodological Research • Instrument Construction and Testing (psychometrics) • Perfecting Research Techniques

  39. METAANALYSIS-synthesis of research findings

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