# Dummy variables question

I don't understand the answer of the first question

1 answers ( 0 marked as helpful)

Suppose you have six categories -- 1, 2, 3, 4, 5, 6. The question is how many variables do you need for these categories? You only need 5. Suppose the variables are is_1, is_2, is_3, is_4, is_5. You can still identify whether someone's in category 6 because that can be picked out by is_1, is_2, is_3, is_4 and is_5 all being 0. So the answer's 5.