Quantitative Research

Experimental Research Categories Randomized Experimental Use of comparison groups Random assignments to groups Quasi-experimental “Manipulates treatments” but doesn’t use randomly assigned treatment groups Used when randomization of groups is impossible Typically has a pretest and posttest Pre-experimental No comparison group No pretest/weak design

Internal Validity Indicates the extent to which the study is free of extraneous or confounding variables or factors that might account for results. i.e., could effects be due to enthusiastic teacher rather than the program under investigation?

Threats to Internal Validity (p.61) Extraneous events Selection Maturation Subject attrition Pretesting (testing) Statistical regression Diffusion of treatment Experimenter effects Treatment fidelity Subject effects Instrumentation

Criteria for Evaluating Is purpose clear? Significant? Review of Lit—Current? Organized? Is hypothesis/question(s) clearly stated? Is method of sampling clear? What was manipulated as independent variable(s) Are procedures for collecting data described fully? Are there any threats to internal validity? Do conclusions/interpretations follow logically from the results? Are limitations indicated? Is experiment so contrived and artificial that the findings have little generalizability?

Class Activity In your content groups, answer the questions (3, 4, 7 & 9) on pp. 71-72 Fill in the Credibility Scorecard on p. 73