' H D I t H D I t 1

Coefficient

Std. Error

t

p > |t|

a0

6.82 × 1021

0.0002543

0.00

1.000

a1

−2.71 × 106

1.38 × 106

−1.97

0.060

a2

−0.5878721

0.0002543

−3.64

0.001

F(2) = 7.14

Prob > F = 0.0032

R2 = 34.60%

Adj. R2 = 29.75%