Essay on A Method For Selecting Variables For A Regression Model

Essay on A Method For Selecting Variables For A Regression Model

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Another common method for selecting variables for a regression model is to look at the univariate relation between each variable and the response, culling only those variables significant for entry into the subsequent regression analysis. It is important to note that this is really nothing more than a variant of automated selection, increasing the probability of overfitting, as well as other problems. An example that Babyak (2004) gives is that variables that are isolated may act differently when compared to variables used simultaneously with 1 or more other variables. This also can have an effect on phantom degrees of freedom, which is not conductive to proper data collection and analysis.
Categorizing variables is yet another pitfall for many researchers. Categorizing a continuously measured predictor will lead to overly optimistic results. We also see that categorizing variables into groups may result in a loss of information, lower measurement precision, and a considerable loss of power in subsequent analyses. While less known but still a common practice is dichotomizing two co...

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