Steam processing of peat. A bioengineer wants to model the (y) of carbohydrate solubilized during steam processing of peat as a function of temperature (x1), exposure time (x2), and pH value (x3). Data collected for each of 15 peat samples were used to it the model.

E(y) = β ₀ + β ₁ x ₁ + β ₂ x2+ β ₃ x ₃

A summary of the regression results follows:

Ŷ = -3,000 + 3.2 x ₁ -4x ₂ -1.1 x ₃ R ² = 0.93

Sβ̂ ₁ = 2.4, Sβ̂ ₂ = 0.6, Sβ̂ ₃ = 0.8

r ₁₂ = 0.92, r ₁₃ = 0.87, r ₂₃ = 0.81

Based on these results, the bioengineer concludes that none of the three independent variable x _1, x ₂ and x ₃ is a useful predictor of carbohydrate amount, y. Do you agree with this statement? Explain.