A dynamic sampling plan among strata is a permutation of sampled items specifying which stratum is to receive the next item to be included in the sample. An optimal such plan has the property of achieving minimum variance for its cost whenever it is truncated. This article shows that optimal dynamic sampling plans exist under very general conditions, and gives a simple algorithm for constructin...

Abstract Reciprocity—the mutual provisioning of support/goods—is a pervasive feature social life. Directed networks provide way to examine the structure reciprocity in community. However, measuring involves assumptions about what relationships matter and how elicit them, which may impact observed reciprocity. In particular, practice aggregating multiple sources data on same relationship (e.g., ...