Confidence intervals for batch properties based on both sampling and analytical variance

Summary If different random samples are taken from a heterogeneous batch and each sample is analysed once or in replicate, the average result is a point estimation of the true but unknown mean of the batch property concerned. In this paper, formulae are given for the numbers of degrees of freedom, which are necessary for interval estimations based on both the sampling and the analytical variance. It is essential to distinguish between situations in which estimates of the variances are available and in which they are not.