How is an analysts coefficient of variation determined?
There are a variety of methods for determining an analyst’s coefficient of variation or intracounter relative standard deviation. This statistic describes the variability of data obtained by a single counter. The NIOSH 7400 method and the AIHA Laboratory Quality Assurance Manual recommend the use of replicate analyses of reference slides to determine the intracounter variability for each fiber-loading range. The OSHA ID-160 method requires the construction of a CV curve. There have also been a number of articles published advocating the use of the recount analyses to determine an analyst’s coefficient of variation for each fiber-loading range. All of these approaches are considered statistically valid and acceptable for AAR program compliance. The analyst’s relative standard deviation (or coefficient of variation) must be determined to properly evaluate the 10 percent recount acceptability. Additional assistance in understanding the statistics involved with all of these approaches may
