I have a question regarding the interpretation of a linear regression output. In my data I have one independent categorical variable (condition) with five values which I represented as four dummy variables (one, two, three, four). Does the output mean that each of the possible four conditions (e.g. one) is compared to the condition five (the excluded one)?
What happens when I exclude four dummy variables and only run the regression with one dummy variable? Does it mean that category one is compared to the rest four possibilities taken together? Does a model like this make sense?