1. One or more computer-readable media storing computer-executable instructions that, when executed by a processor of a computing device, configure the processor to perform acts comprising: receiving a score for each item in an overall population; creating a plurality of sub-populations from the overall population based on the score for each item, each sub-population being more homogenous than the overall population; calculating a precision value and a variance value for each sub-population to determine an overall precision value and an overall variance value for the overall population; and determining if the overall precision value and the overall variance value satisfy a predetermined confidence condition, the predetermined confidence condition being an indication that the overall population is representative of a class of interest.