I have to do a binary logistic regression with a lot of independent variables. Most of them are binary. Few ones are categorical with more than two possible values.
Which is the best way to deal with such variables?
For example, for a variable with three possible values, I suppose that two dummy variables have to be created. Then, in a step-wise regression procedure, it is better to test in the same time both the two dummy variables, or to test them separately?
Since I will use SPSS which I do not remember very well, which way does SPSS operate?
Moreover, for a categorical ordinal variable, it is a good thing to use dummy variables which recreate the ordinal scale (for example, using three dummy variables for a 4-state ordinal variable, put 0-0-0 for level 1, 1-0-0 for level 2, 1-1-0 for level 3 and 1-1-1 for level 4, instead of 0-0-0, 1-0-0, 0-1-0 and 0-0-1 for the 4 levels)?
Thanks for your answers.