A Simplified Variogram Method for Determining the Estimation Error Variance in Sampling from a Continuous Stream

The underlying theory for determining the estimation error variance of the mean of samples taken from a moving stream is reviewed. Situations where standard formulae will give incorrect results are identified and appropriate corrections given for those situations. On the basis of this theory, a simplified method, using only results for a linear variogram, is proposed. The proposed method is shown to work correctly for multistage sampling and also when the variogram itself is varying. Examples are given of the application of the method to determination of the estimation error variance and to the design of sampling schemes.