病人有四个指标：X1：凝血值；X2：预后指数（与年龄相关）；X3：酶化验值；X4肝功能化验值。54位肝病人术前数据与术后生存时间如表所示.病人生存时间的Box-Cox变换变量Z与X1，X2，X3，X4的线性回归模型是合理的，程序实现了如何选择最优回归方程。(Patients have four indexes: X1: coagulation value; x2: prognosis index (related to age); X3: enzyme test value; X4 liver function test value. The data of 54 liver patients before operation and survival time after operation are shown in the table. The linear regression model of box Cox transformation variables Z and x1, X2, X3, X4 of patients' survival time is reasonable. The program realizes how to choose the optimal regression equation.)