1. Research in Communicative Disorders1 Research Design & Measurement Considerations (chap 3) Group Research Design Single Subject Design External Validity Issues Factors Affecting the Measurement Process

2. Research in Communicative Disorders 2 Group Research Design Between Subjects Design Within Subjects Design Mixed Subjects Design

3. Research in Communicative Disorders 3 Between Subjects Design Examines differences between groups of subjects Control and experimental groups –Groups are identical except for variable under question –Randomization and counter-balancing

4. Research in Communicative Disorders 4 Within Subjects Design One group of subjects are examined under two or more conditions. Used often with longitudinal research Problems –Order or learning effect –Carry-over

5. Research in Communicative Disorders 5 Mixed Subjects Design Combination of Between and Within Subject Design. Comparing two or more different variables.

6. Research in Communicative Disorders 6 Single Subject Design Purpose and application Types of Designs –The ABCs Evaluation of Single Subject Design –YOU CAN NOT USE SUMMARY OR INFERENTIAL STATISTICS ON SINGLE SUBJECT DESIGN !

7. Research in Communicative Disorders 7 Single Subject Design Example

8. Research in Communicative Disorders 8 External Validity Issues External validity refers to the ability to generalize from a sample to a population. Can be improved by random sampling techniques and by replication.

9. Research in Communicative Disorders 9 Factors Which Affect the Measurement Process (chap 4) Test environment Instrument calibration Instructions to subjects Observer bias

10. Research in Communicative Disorders 10 Test environment Ambient noise reduced or eliminated Avoid Distractions –Lighting –Temperature –Visual distractions

11. Research in Communicative Disorders 11 Instrument calibration Audiometric equipment (ANSI S3.6-1989) Recording equipment

12. Research in Communicative Disorders 12 Instructions to subjects Clear, concise, and appropriate Use appropriate language Often use a script to insure inter-subject validity and reliability

13. Research in Communicative Disorders 13 Observer Bias Rosenthal Effect –Interactional –Non-interactional

14. Research in Communicative Disorders 14 Measurement Reliability What is reliability? How is it evaluated –Stability (test-retest reliability) –Equivalence –Internal Consistency

15. Research in Communicative Disorders 15 Measurement Validity Content Validity Criterion Validity Construct Validity

16. Research in Communicative Disorders 16 Content Validity This is somewhat subjective. Involves making sure that the content of your procedures are appropriate. No specific tests for content validity … often use peer review for evaluation.

17. Research in Communicative Disorders 17 Criterion Validity Concurrent validity –Ability to correlate to a test of known validity Predictive validity –Attempt to predict performance based on a given test.

18. Research in Communicative Disorders 18 Construct Validity How well a test relates to a theoretical construct. Assumes theory is correct. Specific statistical measurements can be used to evaluate construct validity.

19. Research in Communicative Disorders 19 Efficacy of Treatment Research (chap 5) Factors Affecting Internal Validity Factors Affecting External Validity Protection of Subjects

20. Research in Communicative Disorders 20 Factors Affecting Internal Validity History Maturation Testing Effects Instrumentation Statistical Regression Differential selection of subjects Mortality Hawthorne Effect Interaction of Factors

21. Research in Communicative Disorders 21 History Involves repeated measures. A change in the subject between the measurements. Longitudinal studies most susceptible.

22. Research in Communicative Disorders 22 Maturation Different than “history” since it deals specifically with age. Use control group to factor out maturation effects.

23. Research in Communicative Disorders 23 Testing & Practice Effects The more times you perform a task the better you will become. Can minimize by … –Counterbalancing presentation –Train stubjects Reactive and non-reactive measurements

24. Research in Communicative Disorders 24 Instrumentation Calibration of instrumentation Use of non-standardized tests Observer bias (Rosenthal effect) Test environment

25. Research in Communicative Disorders 25 Statistical Regression Occurs when you create subject groups based on their test scores.

26. Research in Communicative Disorders 26 Differential selection of subjects Can occur with comparative and descriptive research Can use counter balanced groups or random sample. Problems can occur if there is an overlap of a variable.

27. Research in Communicative Disorders 27 Mortality Refers to subjects who drop out of study. Drop outs might be different than remaining subjects. Big problem with surveys and questionaires.

28. Research in Communicative Disorders 28 Hawthorne Effect Subjects change behavior simply because that person knows that they are a subject in a research subject. Can use blind study and double blind study.

29. Research in Communicative Disorders 29 Interaction of Factors

30. Research in Communicative Disorders 30 Factors Affecting External Validity Subject Selection Reactive or Interactive Effects of Pretesting Reactive Arrangements Multiple Treatment Interference

31. Research in Communicative Disorders 31 Subject Selection Generalizing results of the test sample to another another group from a different population. Not only done in research, but done clinically all the time. This is a common problem in the educational setting.

32. Research in Communicative Disorders 32 Reactive or Interactive Effects of Pretesting The administration of a pretest can affect the attitudes by sensitizing the subject.

33. Research in Communicative Disorders 33 Reactive Arrangements Degree to which the setting of the research is reactive or interacts with the independent variable in determing the subject’s performance on the dependent variable.

34. Research in Communicative Disorders 34 Multiple Treatment Interference

35. Research in Communicative Disorders 35 Protection of Subjects Human Research Animal Research Institutional Review Board (IRB)

36. Research in Communicative Disorders 36 Last Slide