topic Is it a sensible practice to collapse categories of a predictor? in Statistical Procedures https://communities.sas.com/t5/Statistical-Procedures/Is-it-a-sensible-practice-to-collapse-categories-of-a-predictor/m-p/61115#M2847 <HTML><HEAD></HEAD><BODY><P>Depends on the context of the data. </P><P></P><P>If for example level 1 is age&lt;30 and level 2 is age between 31 and 60 and level 3 is age &gt;60 then you're simply recoding to age &lt;30 and age&gt;30 which is okay, as long as you don't introduce a bias into your data. </P><P></P><P>If you're combining things that don't make sense ie level 1 is unknown and level 2 is Grade 1 then there it doesn't make sense. </P><P></P><P>Basically, check if it makes logistic sense to collapse them from a business or interpretative perspective and check if the distribution is significantly different with the predictor ( a chi square usually works) to make sure you interpret things correctly. </P><P></P><P>I work in Health Care and we routinely do this.</P></BODY></HTML> Wed, 07 Sep 2011 01:18:10 GMT Reeza 2011-09-07T01:18:10Z Is it a sensible practice to collapse categories of a predictor? https://communities.sas.com/t5/Statistical-Procedures/Is-it-a-sensible-practice-to-collapse-categories-of-a-predictor/m-p/61114#M2846 <HTML><HEAD></HEAD><BODY><P>I used logistic regression to run a model. An explanatory variable called 'location' has 3 levels (1, 2, 3). Level 3 is the reference group. For this analysis, the estimated regression coefficients for level 1 and level 2 are 1.102 and 1.111 respectively. As the values are very close, is it sensible to combine these two levels into a single level to make the model simpler? Or it is better to keep the two levels as what they are separate?</P></BODY></HTML> Wed, 07 Sep 2011 00:32:23 GMT https://communities.sas.com/t5/Statistical-Procedures/Is-it-a-sensible-practice-to-collapse-categories-of-a-predictor/m-p/61114#M2846 Ruth 2011-09-07T00:32:23Z Is it a sensible practice to collapse categories of a predictor? https://communities.sas.com/t5/Statistical-Procedures/Is-it-a-sensible-practice-to-collapse-categories-of-a-predictor/m-p/61115#M2847 <HTML><HEAD></HEAD><BODY><P>Depends on the context of the data. </P><P></P><P>If for example level 1 is age&lt;30 and level 2 is age between 31 and 60 and level 3 is age &gt;60 then you're simply recoding to age &lt;30 and age&gt;30 which is okay, as long as you don't introduce a bias into your data. </P><P></P><P>If you're combining things that don't make sense ie level 1 is unknown and level 2 is Grade 1 then there it doesn't make sense. </P><P></P><P>Basically, check if it makes logistic sense to collapse them from a business or interpretative perspective and check if the distribution is significantly different with the predictor ( a chi square usually works) to make sure you interpret things correctly. </P><P></P><P>I work in Health Care and we routinely do this.</P></BODY></HTML> Wed, 07 Sep 2011 01:18:10 GMT https://communities.sas.com/t5/Statistical-Procedures/Is-it-a-sensible-practice-to-collapse-categories-of-a-predictor/m-p/61115#M2847 Reeza 2011-09-07T01:18:10Z