棉花苗期棉蚜的二项式抽样设计及其精度分析

基于棉花苗期棉蚜（Ａｐｈｉｓ ｇｏｓｓｙｐｉｉ）的２４组调查数据，利用每样方虫口不超过数阈值Ｔ（为０，１，２，…，９，１０，１５，２０，３０）头蚜虫的植株比例（ＰＴ）与种群密度（ｍ，头／株）的关系，拟合经验关系式１ｎ（ｍ）＝α＋ｂ１ｎ〔－１ｎ（ＰＴ）〕设计二项式抽样。通过对不同数阈值Ｔ的决定系数（ｒ＾２）、估计方差（Ｖａｒ（ｍ））和抽样精度（ｄ估计）等进行综合分析，结果表明该蚜虫在数阈值Ｔ为１５时

Binomial sampling plans and the sampling precision analysis for cotton aphid on vegetable stage

Field sampling of cotton aphid, Aphis gossypii , on cotton vegetable stage was conducted in Quzhou, Hebei province in 1991. From the data, estimates of mean aphid density ( m ), variance ( s 2 ) and the proportion of plants ( P T ) with no more than T (=0,1,2,...,9,10,15,20 and 30, respectively) aphids, were calculated (where T is defined as the tally threshold). There were 24 estimates for Aphis gossypii population. The empirical relationship between m and P T was developed using the parameters estimated from the linear regression of ln( m ) on ln-ln( P T )]. The determination coefficients, r 2, prediction variance of m from P T , Var(m), and the sampling precision, denoted as d , obtained with different T values were analysed. The results indicated that the optimal T for this aphid should be 10 when its population density is higher than 10 aphids per plant. The results also showed that the conventional binomial sampling (0-1) method produced unacceptable low levels of sampling precision and thus could not be used in sampling of cotton aphid on cotton vegetable stage.