In the First-Order Model $\hat { y } = 8 + 3 x _ { 1 } + 5 x _ { 2 }$

In the first-order model $\hat { y } = 8 + 3 x _ { 1 } + 5 x _ { 2 }$ ,a unit increase in x₂,while holding x₁ constant,increases the value of y on average by 5 units.