Methods, systems, and apparatus, including computer programs encoded on computer storage media, for evaluating clusters of geographic entities, for example, to be used in a randomized geographic experiment. One method includes using a clustering algorithm to cluster geographic entities into a set of clusters, and identifying whether each geographic entity is an ambiguously classified entity or a definitively classified entity. The method further includes determining a measurement for the set of clusters according to a quantification of an attribute of the definitively classified entities and the ambiguously classified entities. Similar measurements can be calculated for other sets of clusters, and the clusters can be compared according to their measurements.