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Overview
As discussed below, not much can be concluded from one-point-in-time studies of a single group. It is much better to have a comparison (control) group, and better yet to have measurements before (pretest) and after (posttest) the treatment (the change in the causal variable or variables), and best of all to have multiple pretests and posttests. Any given method of data collection, such as survey research, could be used in an experimental or a quasi-experimental design, depending on whether there was a treatment and a control group, and if the participants were randomly assigned. Similarly, analysis of variance (ANOVA) studies may be experimental or quasi-experimental (but originated in the former). More on research design may be found in the sections on univariate GLM (ANOVA, ANCOVA) and multivariate GLM (MANOVA, MANCOVA). In practical terms, however, some methods of data collection, such as case studies, are used almost exclusively in non-experimental designs.
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Copyright 1998, 2008, 2009 by G. David Garson..
Last update 3/19/2009.