两阶群团抽样在森林调查中的估计效率研究

Study on Efficiency of Two-Stage Cluster Sampling in Forest Inventory

从两阶群团抽样的概念入手，根据两阶群团抽样当群团之间不存在差异成分（Ｓβ２＝０）时与系统抽样或简单随机抽样具有相同的抽样效率的性质，定义了误差扩大因子，提出了效率系数的概念，并推导出了效率系数等于１的临界状态的相关系数ｒ＊的表达式，为群团抽样设计和效率评估提供了重要依据。此外，还对群团抽样估计效率与群内样地间距的关系进行了较深入的研究，并用实例进行了说明。最后，对两阶群团抽样在森林调查中的综合效率评价也进行了讨论。

According to the special feature that two-stage cluster sampling has the sameefficiency as the systematic sampling or simple random sampling when there are no differ-ences among clusters,the term of error expansion factor is presented in this paper. Besidesthe correlation coefficient for critical state,when efficiency coefficient equals to l, is formu-lated,which provide important reference of implementing cluster sampling design and sam-pling efficiency assessment.In addition,the relationship between efficiency of two-stage clus-ter sampling and distance between plots in a cluster is further studied with an exampledemonstrated in detail.Finally,the efficiency assessment of two-stage cluster sampling in for-est inventory is also discussed.