Connected with an extensive analysis,it can be concluded that when the regression line gets across the origin,the rate estimator of two sampling methods is equal to the sampling efficiency of regression estimator,when,the sampling efficiency ofis more efficient than the equiprobability sampling,and when and meanwhile,the rate estimator of equiprobability sampling is m.

Three dimension random sampling frame was con-ducted with the mean total product quantity per labor(A),agricultural product price index(B) and the rate of rural industrial labors as three experiment factors;the average ruralnet income per capita as the experinient target.

Because of the frequent changes in the item units to be sampled for enterprises under the quota limit, the sampling frame is rather unstable, which exerts adverse impact on the precision in assessing the samples.

With eight species of unicellular algae cultured in random combinations to construct the assemblages with different degrees of richness,the increase pattern of colony biomass with the change of species richness was investigated,and the sampling effect was detected by using multiple variance analysis(MANOVA) method.

The interpretation of these experiments, however, has been controver-sial because two types of mechanisms," niche complementarity" and" sampling effect", may operate.