The Following MINITAB Output Presents a Multiple Regression Equatior $\hat { y }$

Multiple Choice

The following MINITAB output presents a multiple regression equatior $\hat { y }$ =b₀+b₁x₁+b₂x₂+b₃x₃+b₄x₄
The regression equation is
$$\mathrm { Y } = 4.7712 + 0.2662 \mathrm { X } 1 + 1.2710 \mathrm { X } 2 - 1.1349 \mathrm { X } 3 - 1.8545 \mathrm { X } 4$$
$\begin{array}{lllll}\text { Predictor } & \text { Coef } & \text { SE Coef } & \text { T } & \mathrm{P} \\\text { Constant } & 4.7712 & 0.7648 & 0.92800 & 0.3280 \\\mathrm{X} 1 & 0.2662 & 0.8036 & -0.93740 & 0.3570 \\\mathrm{X} 2 & 1.2710 & 0.8451 & 1.74170 & 0.0830 \\\mathrm{X} 3 & -1.1349 & 0.6318 & -2.94990 & 0.0080 \\\mathrm{X} 4 & -1.8545 & 0.6753 & 3.27200 & 0.0020\end{array}$



$\text { Analysis of Variance }$
$\begin{array}{lccccc}\text { Source } & \text { DF } & \text { SS } & \text { MS } & \text { F } & \text { P } \\\text { Regression } & 4 & 624.2 & 156.1 & 9.8797 & 0.003 \\\text { Residual Error } & 40 & 633.7 & 15.8 & & \\\text { Total } & 44 & 1,257.9 & & & \\\hline\end{array}$


It is desired to drop one of the explanatory variables. Which of the following is the most appropriate action?

A) Drop x₄, then see whether R² increases
B) Drop x₁, then see whether R² increases
C) Drop x₄, then see whether adjusted R² increases
D) Drop x₁, then see whether adjusted R² increases