Marianne Toft, Statistician, Novozymes
Some of our products are bacterial spores, for which the assay used from early development to product release involves counting bacterial colonies on agar plates – the response being the number of colony forming units (CFU) per gram of product. This presentation will show some studies made during optimisation of such an assay. The statistical distribution of CFU data is discussed, and CV estimation involving several sources of variation is presented. This involves mixed linear models with a hierarchical structure of nested random factors.
