Method	$β_{i n t}$	$β_{x_{1}}$	$β_{x_{2}}$	$β_{x_{3}}$	$β_{x_{1} x_{2}}$	$β_{x_{1} x_{3}}$	$β_{x_{2} x_{3}}$	$β_{x_{1}^{2}}$	$β_{x_{2}^{2}}$	$β_{x_{3}^{2}}$
Backward	13.1263	−0.1894	0.8783	−0.7094	−0.1749	0	0	0	−0.5926	0
	(0.3821)	(0.0774)	(0.0775)	(0.0775)	(0.0925)	(−)	(−)	(−)	(0.1463)	(−)
ALASSO	13.1183	−0.1894	0.8783	−0.7092	−0.1874	0	0.1795	0	−0.4754	0
	(0.3633)	(0.0824)	(0.0746)	(0.0737)	(0.0875)	(−)	(0.0837)	(−)	(0.1598)	(−)
LARS	13.1249	−0.1894	0.8783	−0.7094	0	0	0	0	−0.5904	0
	(0.3634)	(0.0846)	(0.0846)	(0.0846)	(−)	(−)	(−)	(−)	(0.1713)	(−)
GLS	13.1960	−0.1894	0.8783	−0.7094	0	0	0	0	−0.4303	0
	(0.3910)	(0.0734)	(0.0734)	(0.0734)	(−)	(−)	(−)	(−)	(0.1877)	(−)