NOTE: A finite difference approximation is used for the derivative of the PDF function at 行 424
      列 45.
NOTE: GCONV convergence criterion satisfied.
NOTE: At least one element of the (projected) gradient is greater than 1e-3.
WARNING: The final Hessian matrix is full rank but has at least one negative eigenvalue.
         Second-order optimality condition violated.
NOTE: 数据集 WORK.NB0COUT 有 2812 个观测和 2 个变量。
NOTE: “PROCEDURE NLMIXED”所用时间（总处理时间）:
      实际时间          4.28 秒
      CPU 时间          4.34 秒

proc nlmixed出现如下结果，那么估计的参数还可信吗？我用proc countreg却没有问题？这是为什么呢？