验证克拉默不等式，也就是使得无偏估计量的方差达到一个下限。这时就要首先得到一个随机的无偏估计量，然后计算出其方差并绘制图形，最后绘制克拉默的界限图。-Verify Cramer inequality, which is so unbiased estimators of variance reaches a limit. Then we must first obtain a random unbiased estimator, then calculate its variance and g