Equivalence of Two Estimates of Product Variance

IT is frequently necessary to know the variance of a product apart from measurement variance. Grubbs [3] has obtained an estimate of product variance by a covariance technique for the case where two or more methods are used to measure each item sampled from a population. The components of variance estimate of the product variance from the analysis of variance has occurred frequently in the literature [1]. A proof of the equivalence of Grubbs' covariance estimate and the components of variance estimate of the product variance is presented. Use of the product variance estimate by Grubbs' method is subject to the same conditions and assumptions imposed upon the general two-way model.