I am building a linear regression model and have a few categorical predictors. I have created (#levels - 1)dummy/indicator variables for each of the categorical covariates. Lets say the variable is temp = ( hot, moderate, cold ). I have created 2 dummy variables for hot and cold.
My doubt is in the model, can i have just have one of the indicator variables in the model or is it a all or none way of including categorical variables.
I have used backward elimination method and in the final model i am getting just dummy variable corresponding to hot. Can i use this model or should i ensure that either both the dummy variables are present or none.
Appreciate the help.