Evaluating a Control Variable By Daniel Palazzolo, Ph.D. ( printable version here ) We need to go through a few steps to assess the effects of a control variable. 1. Test a bivariate relationship —referred to as the “original relationship.” It must be statistically significant and at least re 2. Consider a control variable , either by theory or deductive logic, that seems to provide an alternative explanation for th 3. Assess the impact of the control variabl e. This involves comparing the results for each value of the control variable w 4. Write the results in clear, commonsense terms , i.e. identifying the effects of the control variable but relating the valu Scenario 1: Spurious. The control variable renders the original relationship insignificant. Column %: Column percentages grow closer together for all values of the control variable, to the point that there no longer Strength Measure : Measures are much weaker, approximating zero for all values of the control variable. Significance
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