逐步判别分析法在筛选水质评价因子中的应用

应用逐步判别分析法对水质进行评价因子筛选，通过对水质实际监测因子的假设检验分析，引入判别能力好的因子，建立判别方程。对实例评价结果表明：通过筛选引入判别方程变量的后验概率均达到90%以上，对判别分类有显著影响，从而提高了所建立的判别函数的稳定性和评价结果的可靠性。进行因子筛选的评价结果显示石头口门水库2001-2004年为Ⅱ类水，2005年为Ⅲ类水，污染呈现出逐年加重之势，与实际情况相符；而未进行因子筛选的评价结果显示5年水质没有变化，均为Ⅱ类水，且2005年后验概率仅达到52％，结果判误率高。

Application of Stepwise Discriminant Analytical Method in Screening Factor in the Water Quality Evaluation

Screen the factors of water quality evaluation through the stepwise discriminant analysis method. By hypothesis-testing analysis of the monitoring water quality factors, lead in the most effective factors and establish the discriminant equation. Then the evaluation results of the water quality of an example showed that the posterior probability of factors are over 90% and have a significant impact on the identification and classification. The stability of the established discriminant function and the reliability of the results of the evaluation were enhanced. The appraisal result of the water quality of Shitoukoumen reservoir is Ⅱ from year 2001 to 2004,and it is Ⅲ in 2005. Accord with the fact pollution has shown increasing trend year by year，in line with the facts. The appraisal result of water quality without the variable screening is Ⅱ in 2005，and the posterior probability is about 52%, the result shows the error rate is high.