how rapidminer regard categorical variable in logistic regression?

Hi, 

I ran logistic regression. the dependent variable is 'IDKC WS_10', which has two categories, W and M. I used six independent variables, and one of them is categorical variables: 'IDKC WS_3' (W /M).

1 ) I wonder how the rapidminer calculate confidence with the combination of categorical and continuous variable. I didn't set any reference group (how to do this actually?).

2) I wonder how the rapidminer convert or regard the categorical variable when it shows the logistic equation. How can I write the equation with using the coefficient for the categorical variable?