Quantitative Research Experimental Research Categories Randomized Experimental Use

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