Our last blog on this topic discussed improved biological efficiency by design. Today we will discuss the statistical corrections for viable particle reading accuracy.
The values in each table are calculated from Feller’s formula (Feller, 1950):
Pr = N [1/N + 1/N – 1 + 1/N – 2 + 1/N – r + 1].
The calculation is performed using flow rates of 25–50 L/min and 100 L/min (used by the Biocapt Impactor). Where:
- Pr is the probable statistical total of viable particles required to produce r positive holes
- N is the number of holes
- r is the number of viable particles counted on the agar plate
Example: for flow rates of 25–50 L/min, the design of the BioCapt Impactor shows that no correction is necessary until after 57 viable particles in the r and Pr columns.
The BioCapt Impactor uses precision-cut slits to ensure laminar flow and improve biological collection efficiencies for viable particles in accordance with ISO 14698-1/Annex B.
Learn more now by downloading this paper, Table of statistical corrections according to Feller for the BioCapt® Microbial Impactor in microbial air sampling.