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Seasonal cycles, environmental change and BACI designs
Author(s) -
Roberts E. A.
Publication year - 1993
Publication title -
environmetrics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.68
H-Index - 58
eISSN - 1099-095X
pISSN - 1180-4009
DOI - 10.1002/env.3170040205
Subject(s) - changeover , statistics , residual , environmental science , sampling (signal processing) , analysis of covariance , mathematics , computer science , filter (signal processing) , algorithm , transmission (telecommunications) , computer vision , telecommunications
The three largest sewage treatment plants (STP) in Sydney were changed from cliff‐face outfalls to deepwater ones between September 1990 and August 1991. The densities of faecal coliforms at Malabar, a test beach, and at Cronulla, a comparison beach, during the last two years before and the first year after the changeover at Malabar STP were used to study methods of analysing data from this type of study. A factorial‐type analysis of variance based on beaches, years and sampling dates during the year as factors was used to estimate the residual variance and to test for change in level of the densities. The residual variance was estimated from the deviations from a periodic regression of density on day of the year. A covariance analysis of the densities at Malabar with those at Cronulla as covariates gave an appropriate statistical analysis. However, there was little difference between the densities at Cronulla before and after the changeover and the simple difference between the densities at Malabar before and after gave the most efficient estimate of change.