Building a logistic regression model with three categorical features and one continuous. For simplicity, let's say I have the following features and variables:
Feature | Variable
========================================
Gender | Male
----------------------------------------
Weight | Weight (continuous)
----------------------------------------
Income Bucket | 0 - 50k
Income Bucket | 51k - 75k
Income Bucket | 76k - 100k
Income Bucket | 101k - 150k
----------------------------------------
Continent | North America
Continent | South America
Continent | Europe
Continent | Asia
Continent | Africa
Continent | Australia
Recall that I am using for the number of variables so there is no variable for Gender = Female, Income Bucket = 100k+, or Continent = Antarctica.
- if I run this through a multicollinearity check and get VIFs for one categorical variable being higher than 10, does it make sense to remove it?
For example:
Feature | Variable | VIF |
=================================================
Gender | Male | 2
-------------------------------------------------
Weight | Weight (continuous) | 1
-------------------------------------------------
Income Bucket | 0 - 50k | 3
Income Bucket | 51k - 75k | 4
Income Bucket | 76k - 100k | 11 <--
Income Bucket | 101k - 150k | 1
-------------------------------------------------
Continent | North America | 2
Continent | South America | 3
Continent | Europe | 4
Continent | Asia | 1
Continent | Africa | 1
Continent | Australia | 2
Should I drop the categorical variable for Income Bucket = 76k- 100k and then proceed to further model selection?
- Furthermore, does it make sense if one or more (but not all) have p-values are not significant?
For example:
Feature | Variable | P-Value |
=====================================================
Gender | Male | 0.002
-----------------------------------------------------
Weight | Weight (continuous) | 0.001
-----------------------------------------------------
Income Bucket | 0 - 50k | 0.05
Income Bucket | 51k - 75k | 1.65 <--
Income Bucket | 76k - 100k | 0.03
Income Bucket | 101k - 150k | 0.002
-----------------------------------------------------
Continent | North America | 0.05
Continent | South America | 0.001
Continent | Europe | 11.2 <--
Continent | Asia | 0.01
Continent | Africa | 0.09
Continent | Australia | 0.1
Here, does it make sense to drop Income Bucket = 51k - 75k and Continent = Europe based on the P-values?
- How does the "missing" categorical variable (the one removed due to the rule) become interpreted once you drop a few of the ones that are included?
Remember that this is for a logistic regression but I am okay with knowing how it would work for linear as well. And would another method be more suited for this?
Thank you!