Temperature (˚C)

Regression Equation

R²

S

20

y = ?1.164 − 0.178x₁ + 0.1697x₂ + 0.00933− 0.001542+ 0.000375x₁x₂

0.9835

0.1621

30

y = −0.42 + 0.214x₁ + 0.0460x₂ + 0.00011+ 0.000111− 0.00013x₁x₂

0.9435

0.3678

40

y = 10.88 − 1.845x₁ + 0.1862x₂ + 0.07178− 0.002431+ 0.0064x₁x₂

0.9864

0.4208