(ANCOVA- ).
ANCOVA - , :
y = α + β 1 x + β 2 d + ε. (4.40)
, , y , x , d , . .
:
M (x, d = 0) = α + β 1 x + β 2 0 = α + β 1 x . (4.41)
M (x, d = 1) = α + β 1 x + β 2 1 = (α + β 2) + β 1 x . (4.42)
. β 1. (4.41), (4.42) β 2. t - α (α + β 2), , . , , , . , β 2 > 0 , β 2 < 0 .
, . , ? ,
y = α + β 1 x + β 2 d 1 + β 3 d 2+ ε. (4.43)
d 1 d 2 : d 2 = 1 d 1. , β 2 β 3 . (4.40). , :
, ( - 1) .
, .
. . , (4.40) , :
β 1 .
, d = 0, . , .
β 1 (4.40) , . . , , , .
|
|
, , . , , , , : , . , . , :
y = α + β 1 x + β 2 d 1 + β 3 d 2+ ε. (4.44)
y - . x - .
, .
:
M (x, d 1 = 0, d 2 = 0) = α + β 1 x. (4.45)
:
M (x, d 1 = 1, d 2 = 0) = α + β 1 x + β 21 + β 30 = (α + β 2) + β 1 x. (4.46)
:
M (x, d 1 = 1, d 2 = 1) = α + β 1 x + β 21 + β 31 = (α + β 2 + β 3) + β 1 x. (4.47)
β 2, β 3 . . (4.44) β 2, β 3 t -. , , .