1. Choosing a Design Pseudoexperimental and True Experimental Designs

2. Research Designs zExperimental designs are concerned with the manipulation of the IV and the measurement of its effect on the DV zDescriptive designs are concerned with the classification of the subjects and with the application of measurement procedures to subjects in order to assess group differences, developmental trends, or relationships among variables.

3. Research Designs zBoth experimental and descriptive designs are classified as between- subjects, within-subjects, or mixed designs ythe selection of a design depends largely on the research question

4. Between-Subject Designs zIn experimental designs, different groups of Ss are exposed to different IVs ythe IV is applied to one group (exp) but not to the other group (control) zThe major threat to internal validity is subject selection ydifferences may be Ss selection differences rather than the IV y2 ways to equate experimental and control groups: xrandomization xmatching

5. Between-Subject Designs zIn descriptive designs, different groups of Ss are compared with each other with regard to their performance on some criterion variable ythe important thing with descriptive designs is to select Ss who fall distinctly into the different categories of the classification variable but who are otherwise equivalent with regard to extraneous variables xclassifications must be constructed that are mutually exclusive

6. Within-Subjects Designs zThe performance of the same subjects is compared in different conditions. zIn experimental research, the subjects are exposed to all treatment or levels of the IV ybasic concern with these designs is that all conditions should be equivalent except for the application of the IV ytherefore, it is important to control for sequencing or order effect

7. Within-Subjects Designs zThere are 2 ways to control for the sequencing effect: yrandomization xpresentation of the experimental treatment conditions (IV) is randomly sequenced ycounterbalancing xarrange all possible sequences of treatments (IV) and then randomly assign subjects to each sequence

8. Within-Subjects Designs zIn descriptive research, longitudinal studies would be a within-subjects design

9. Mixed Designs zOne IV may be studied with a between- subjects design while another IV is studied with a within-subjects design ythis is a mixed design

10. Research Designs zTwo ways to improve generalizability of findings with research designs: yrandom sampling of subjects yreplication

11. Types of Experimental Designs zPseudoexperimental designs (aka “pre- experimental”) ydo not have built-in controls ythere may be several explanations for the changes in the DV that are not solely caused by the IV yall of these designs have uncontrolled extraneous variables that threaten the internal validity of the experiment yweaker designs zTrue experimental designs

12. Types of Pseudoexperimental Designs zOne-shot case study zOne-group pretest-posttest zStatic group comparison

13. One-shot case study zA descriptive study that has big weakness of no control yno comparisons can be made with this study ystatistics: mainly descriptive statistics (e.g., means); some inferential statistics (e.g., correlation coefficients)

14. One-group pretest-posttest zObservations are made before and after the IV has been administered to the group ybetter than one shot case study, but still problem with 6 possible uncontrolled extraneous variables (history, maturation, testing, instrumentation, statistical regression, mortality) ystatistics: parametric t-test for correlated samples; nonparametric sign test

15. Static group comparison zComparisons are made between one group which is exposed to the IV and one group which is not yno pretest to compare posttest scores yno way to ensure equivalence between groups on relevant extraneous variables yproblems may arise from subject selection variables, testing, instrumentation, mortality ystatistics: parametric t-test; Mann-Whitney U test; chi-square

16. True Experimental Designs zPretest-Posttest Control Group zPosttest-Only Control Group zSolomon Four-Group Design

17. Pretest-Posttest Control Group z2 groups of Ss are compared on a measurement or observation on the DV. yBoth groups are measured or observed twice yfirst measurement serves as the pretest and second measurement serves as the posttest yhalf of the Ss are randomly assigned to the first group while the second half are assigned to second group

18. Pretest-Posttest Control Group zOnly threats to internal validity are testing and mortality zstatistics: independent t-test to compare the two groups; analysis of covariance

19. Posttest-Only Control Group zIdentical to the pretest-posttest control group design except that the pretest is not administered to either of the two groups yby random assignment of Ss to the two groups, it controls selection, history, maturation, and statistical regression ytesting and instrumentation do no exist since none of the Ss is measured twice ymortality could be an internal validity problem

20. Solomon Four-Group Design zSubjects are randomly assigned to four different groups ytwo of the groups receive the treatment (IV) ytwo of the groups do not receive the treatment yonly one of the control groups is administered the pre-test yall four groups are administered the posttest

21. Solomon Four-Group Design zIt is a combination of the pretest-posttest and posttest-only control group designs zit controls for all threats to internal validity zstatistics: 2-way ANOVA

22. What’s Coming Up …. z Human Subject Certification test (next week) z Group Work (next week) z Specific Group Designs (2 weeks) z Single-subject Designs (3 weeks) z Intro/Methods (Oct. 28) z JOURNAL CLUB (Nov 4) z Statistics ydescriptive yinferential z Miscellaneous yinterpreting research yrole of research in CDIS

23. SLP Journal Club z 9 groups y8 groups with 3 members y1 group with 2 members z one group presentation/week z recommendation: select article based on your research project

24. AUD Journal Club z 2 groups y2 groups with 2 members z one group presentation/week z recommend select article from research project