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Relationship between Correlations of Repeated Measurements and Correlations of Relative Standard Deviation Estimates of These Measurements; Application to Proficiency Analytical Testing Program Silica and Asbestos Data.

PB2003100573

Publication Date	2002
Personal Author	Shulman, S. A.
Page Count	28
Abstract	In proficiency testing for analytical methods, participating laboratories at times make determinations of the amount of analysis in test samples. At later times they are given different samples of the same analysis, and make new determinations. If there is interest in studying the relative standard deviation (=CV=standard deviation/mean), also known as relative standard deviation, of the determinations over time, it is necessary to assess the correlation among the CVs. Although there may be substantial correlation between determinations by the same lab in different rounds, the correlation between the relative standard deviations of determinations in those two rounds is often much smaller.
Keywords	Silica Asbestos Statistical models Laboratory tests Covariance Variance Correlation Coefficients Coefficient of variance
Source Agency	National Institute for Occupational Safety and Health
Corporate Authors	National Inst. for Occupational Safety and Health, Cincinnati, OH.
Document Type	Technical Report
NTIS Issue Number	200303

Relationship between Correlations of Repeated Measurements and Correlations of Relative Standard Deviation Estimates of These Measurements; Application to Proficiency Analytical Testing Program Silica and Asbestos Data.

Relationship between Correlations of Repeated Measurements and Correlations of Relative Standard Deviation Estimates of These Measurements; Application to Proficiency Analytical Testing Program Silica and Asbestos Data.
PB2003100573

Publication Date	2002
Personal Author	Shulman, S. A.
Page Count	28
Abstract	In proficiency testing for analytical methods, participating laboratories at times make determinations of the amount of analysis in test samples. At later times they are given different samples of the same analysis, and make new determinations. If there is interest in studying the relative standard deviation (=CV=standard deviation/mean), also known as relative standard deviation, of the determinations over time, it is necessary to assess the correlation among the CVs. Although there may be substantial correlation between determinations by the same lab in different rounds, the correlation between the relative standard deviations of determinations in those two rounds is often much smaller.
Keywords	Silica Asbestos Statistical models Laboratory tests Covariance Variance Correlation Coefficients Coefficient of variance
Source Agency	National Institute for Occupational Safety and Health
Corporate Authors	National Inst. for Occupational Safety and Health, Cincinnati, OH.
Document Type	Technical Report
NTIS Issue Number	200303