A regional planner is studying the demographics in a region of a particular state. She has gathered the following data on nine counties.

County Median Income Median Age Coastal
A $48,157 57.7 1
B 48,568 60.7 1
C 46,816 47.9 1
D 34,876 38.4 0
E 35,478 42.8 0
F 34,465 35.4 0
G 35,026 39.5 0
H 38,599 65.6 0
J 33,315 27.0 0

a. Which variable is the "dependent" variable?