Variables and Qualitative Research

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Extraneous Variables are undesirable variables that influence the relationship between the variables that an experimenter is examining. They exist in all studies and can affect the measurement of study variables and the relationships among these variables. Because of this, they are of primary concern in quantitative studies because they can interfere with obtaining a clear understanding of the relational or causal dynamics within these studies (Burns & Grove, 2011). Another way to think of it is they are variables that could possibly influence the outcome of an experiment, though they are not the variables of actually of interest. A major goal in research design is to decrease or control the influence of extraneous variables as much as possible. Controlling extraneous variables enables the researcher to more accurately determine the effect of an independent or treatment variable on a dependent or outcome variable. Researchers attempt to recognize and control as many extraneous variables as possible in quasi-experimental and experimental studies, and specific designs and sample criteria have been developed to control the influence of extraneous variables that might influence the outcomes of studies (Burns & Grove, 2011). One way to do this is by narrowly defining the sampling criteria to make the sample as homogeneous (or similar) as possible to control for extraneous variables. Other methods include randomization or random assignment of subjects to groups; matching subjects on extraneous variables and then assigning them randomly to groups; application of statistical techniques of analysis of covariance; and balancing means and standard deviations of groups (Mcleod,
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