Answer: b. 3
Step-by-step explanation:
We know that , the indicator variable is a dummy variable in regression analysis which is used to denote either presence ( by 1 ) or absence ( by 0 ) of a nominal variable that can be responsible for the change in output.
Number of indicator variables = (all levels in the original variable)-1
Here , the given categories as per the location are northeast, northwest, southeast, or southwest.
i.e. all levels in the original variable = 4
Then, the umber of indicator variables we need = 4-1 =3
Hence, we need 3 indicator variables.
Thus , the correct answer is b. 3.