In this paper it not only gives the method of unequalprobability in group sampling and unbiassedness of mean estimation and also gives the variance and its unbiassedness of estimation.
本文给出了集团抽样的不等概方法和均值的无偏估计，同时也给出了这种估计的方差及方差的无偏估计。
2
In this paper a probability model of unequal step difference grid had been used to exodus method.