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Reliability of MPN Indexes of Coliform Organisms
The MPN method is accepted for estimating the coliform population in water, and is set forth in Standard Methods. Analyses of variance procedures are available in elementary texts on statistical methods. These two standard procedures were combined to study the interpretation of MPN values. Shortly after the beginning of this study, a similar project was undertaken by J. A. McCarthy, chief of the Lawrence, Massachusetts, Experiment Station. The data from Lawrence were made available for comparison. As a result of the experimental and statistical evidence obtained, it is possible for bacteriologists to: have more confidence in their data; compare the reliability of data from different laboratories working with the same general type of source material; realize that unusual fluctuations in coliform indexes may be caused by factors other than laboratory technique; and, determine, more effectively, the characteristics of the environmental changes that cause these fluctuations. The use of duplicate MPN determinations from the same source is the most important change in procedure introduced in both projects. The customary examination of individual MPN's and their averages was not made. The use of duplicate MPN's and duplicate samples, however, made it possible to investigate the variation characteristic of successive steps in the sampling and laboratory techniques. These techniques and methods of interpretation made it possible to detect changes in the coliform population and to interpret the changes more effectively.
Reliability of MPN Indexes of Coliform Organisms
The MPN method is accepted for estimating the coliform population in water, and is set forth in Standard Methods. Analyses of variance procedures are available in elementary texts on statistical methods. These two standard procedures were combined to study the interpretation of MPN values. Shortly after the beginning of this study, a similar project was undertaken by J. A. McCarthy, chief of the Lawrence, Massachusetts, Experiment Station. The data from Lawrence were made available for comparison. As a result of the experimental and statistical evidence obtained, it is possible for bacteriologists to: have more confidence in their data; compare the reliability of data from different laboratories working with the same general type of source material; realize that unusual fluctuations in coliform indexes may be caused by factors other than laboratory technique; and, determine, more effectively, the characteristics of the environmental changes that cause these fluctuations. The use of duplicate MPN determinations from the same source is the most important change in procedure introduced in both projects. The customary examination of individual MPN's and their averages was not made. The use of duplicate MPN's and duplicate samples, however, made it possible to investigate the variation characteristic of successive steps in the sampling and laboratory techniques. These techniques and methods of interpretation made it possible to detect changes in the coliform population and to interpret the changes more effectively.
Reliability of MPN Indexes of Coliform Organisms
Noble, Ralph E. (author)
Journal ‐ American Water Works Association ; 52 ; 803-814
1960-06-01
12 pages
Article (Journal)
Electronic Resource
English
Statistics , Massachusetts , Sampling , Bacteria , Lawrence , Coliforms , Standards
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