On Estimating Precision of Measuring Instruments and Product Variability

A measurement or observed value is discussed as the sum of two components—one the absolute value of the characteristic measured and the other an error of measurement. The variation in absolute values of the characteristic or items measured is termed product variability, whereas the variation in errors of measurement of an instrument is called the precision or reproducibility of measurement. Techniques are given for separating and estimating product variability and precision of measurement. Comparisons of the various techniques are also discussed for cases involving two or more instruments.