The National Agricultural Statistics Service (NASS) plans to use estimation strategies of increasing complexity in the future and will need to estimate the variances resulting from those strategies. This report describes a relatively simple method of variance/mean squared error estimation, the delete-agroup jackknife, that can be used meaningfully in a remarkably broad range of settings employing complex estimation strategies. The text describes a number of applications of the method in abstract terms. It goes on to shows how the delete-a-group jackknife has been applied to some recent NASS surveys.