AWWA WQTC71481

This paper presents a case study for the validation of a new method for detecting coliphage in groundwater samples. Coliphage is one of the microbial indicators that can be used to monitor fecal contamination under the Ground Water Rule. This paper describes the statistical considerations required in the design of a validation study for the alternative test procedure (ATP) and performance based measurements system (PBMS) approaches. The paper evaluates the number of comparisons necessary to demonstrate equivalence or acceptability by the two approaches. Results of validation were used to demonstrate the relationship between sample size and the confidence intervals around recoveries, sensitivity (true positives), specificity (true negatives), false positives and false negatives between methods. This was contrasted with the relationship between sample size and the ability to detect differences between methods using the ATP method. The design and results of an inter-laboratory validation study are presented, focusing on the sample sizes required and the differences that can be detected between laboratories. Includes 2 references, tables, figures.