-10-
8-
-6
4
2
이
2
4-
N-
4
6
8
10
12
14
16
(a) $\beta_0 > 0, \beta_1 > 0, \beta_2 > 0, \beta_3 > 0$
(b) $\beta_0 > 0, \beta_1 < 0, \beta_2 > 0, \beta_3 < 0$
(c) $\beta_0 > 0, \beta_1 > 0, \beta_2 > 0, \beta_3 < 0$
(d) $\beta_0 > 0, \beta_1 < 0, \beta_2 > 0, \beta_3 > 0$