Censored data regression: Statistical methods for analyzing Secchi transparency in shallow systems
Censored data regression: Statistical methods for analyzing Secchi transparency in shallow systems
复制标题
截尾数据回归：浅层系统中 Secchi 透明度分析的统计方法
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
J. Carstensen
中科院分区：
文献类型：
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作者：
J. Carstensen
在浅水生态系统中的塞奇深度监测偶尔会记录到底部的景象，因此真实的塞奇深度大于观测值。在这种情况下，对Secchi深度数据进行删失。尽管分析这种截尾数据的统计方法已经存在了几十年，并已被广泛用于其他学科，截尾问题已被完全忽视，在水生生态学。在这里，我介绍并举例说明了一种专门针对删失数据的统计回归技术（删失数据回归，CDR），并将塞奇深度分布的平均值和标准误差的估计值与文献中常用的统计方法进行了比较。随着删失数据比例的增加，标准方法越来越低估了Secchi深度的平均值和标准误差。测量Secchi深度的分析，从四个沿海站点在丹麦，代表29%至80%的删失数据，记录了大量的偏差分布均值（高达2米），和标准误差（50%）时，删失不占。这对估计塞奇深度的趋势和季节性模式产生了重大影响，在最坏的情况下，实际上没有报告任何重大趋势，而实际上存在一种趋势。因此，有必要引入CDR作为一个更合适的方法来分析在浅水湖泊和沿海生态系统的Secchi深度。更一般地说，本研究的目的是提高人们对审查问题的认识，并促进适当的统计方法来分析审查的生态数据。
Secchi depth monitoring in shallow ecosystems occasionally records sight to the bottom and thus the true Secchi depth is larger than the observed. In such cases Secchi depth data are censored. Despite that statistical methods for analyzing such censored data have existed for many decades and have been widely used in other disciplines, the censoring problem has been completely overlooked in aquatic ecology. Here, I have presented and exemplified a statistical regression technique (Censored Data Regression, CDR) that specifically addresses censored data, and compared resulting estimates of mean and standard error of Secchi depth distributions with those of statistical methods commonly applied in the literature. Standard methods increasingly underestimated both mean and standard error of Secchi depths as the proportion of censored data increased. Analysis of measured Secchi depths from four coastal sites in Denmark, representing 29% to 80% censored data, documented substantial biases in distribution means (up to 2 m), and standard errors (50 %) when censoring was not accounted for. This had significant repercussions for the estimation of trends and seasonal patterns of Secchi depths, in the worst case actually reporting no significant trend when a trend was actually present. Consequently, there is a need to introduce CDR as a more appropriate method for analyzing Secchi depths in shallow lakes and coastal ecosystems. More generally, the objective of this study was to raise the awareness of the censoring problem and to promote appropriate statistical methods for analyzing censored ecological data.