Temperature (˚C)

Regression Equation

R²

S

20

y = −0.0137 − 0.00231x₁ + 0.002206x₂ + 0.000121− 0.000020+ 0.000005x₁x₂

0.9818

0.0022

30

y = −0.0041 + 0.00281x₁ + 0.00006x₂ + 0.000001+ 0.000001− 0.000002x₁x₂

0.9425

0.0048

40

y = 0.1433 − 0.02402x₁ + 0.002418x₂ + 0.000934− 0.000032+ 0.000084x₁x₂

0.9864

0.0054