UNCW EDN 523 - Experimental Designs (13 pages)

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Experimental Designs



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Experimental Designs

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Pages:
13
School:
University of North Carolina Wilmington
Course:
Edn 523 - Research In Education

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1 EDN 523 Martin Kozlof Experimental Designs and Internal and External Validity This paper has three sections Section I provides a legend of the symbols used in describing experiments Section II describes pre experimental designs true experimental designs and quasi experimental designs Section III describes threats to internal and external validity It might be a good idea to skim Section III first I LEGEND X exposure of a group or an individual e g in a single subject design to experimental i e independent variables i e events conditions or treatments The experimenter may or may not have control over this exposure O observation or measurement Were the validity and reliability of instruments and measurement established prior to use Was observer reliability checked periodically during the experiment Left to right dimension time order X s and O x in a vertical line mean that observation and exposure to or change in experimental variables occur simultaneously R random assignment to comparison groups Was matching used to make groups more equivalent on certain variables Or was randomization used to give all possibly contaminating extraneous variables an equal chance to be in all groups Was the equivalence of comparison groups assessed pior to or after a pre test II DESIGNS PRE EXPERIMENTAL EXPERIMENTAL AND QUASIEXPERIMENTAL A Pre experimental Designs Pre experimental designs have either no comparison groups or comparison groups whose equivalence is indeterminate 1 2 1 One shot Case Study In this design there is almost complete absence of control over or at least a determination of extraneous variables that might account for the findings Since there is no pre test and no comparison group inferences that X had an effect are based upon a comparison between the one case studied and other cases observed and remembered That is a causal inference that X has an effect on the dependent variables observed is based on general expectations of what the data would have been had X not



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