Threats to Internal and External Validity - Essay Example


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Threats to Internal and External Validity

On the other hand, factors affecting external validity ask whether or not the conclusions of the research are replicable over diverse populations. Here are some examples of threats to validity of an experiment. Threats to Internal Validity The first one is history. Events may occur during the course of the experiment that affect the experimental results. This contemplates an outside or external event that impacts on the dependent variable. Campbell defines it as “the specific events occurring between the first and second measurement in addition to the experimental variable.” (Campbell and Stanley, 5). If Dr. Williams wants to ensure that there is no threat pertaining to history affecting the outcomes, then there must be nothing coming in between the first and second measurement, ie., an unforeseeable humanitarian crisis that would congest the hospitals. A second example is maturation. People are continually growing and changing, whether in an experiment or not, and these changes affect the result of the experiment. To distinguish from history, maturation is the processes within the subjects, not in their external environments. ...
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THREATS TO THE VALIDITY OF AN EXPERIMENT Firstly, we begin by clarifying what we mean by threats to validity. Maxfield and Babble (2005) put it in very simple terms: these are, according to them, “possible ways that a researcher might be wrong in inferring causation…
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