1. A method comprising: accessing a trained computer model that predicts membership in a group; receiving a set of calibration data items, each calibration data item having a known membership in the group; applying a computer model to each of the calibration data items, the output of the computer model generating a calibration value for each of the calibration data items that represents a predicted probability of membership in the group; receiving a test data item having an unknown membership in the group; applying the computer model to the received test data item to generate a test output value, the test output value reflecting a predictive probability by the computer model of membership in the group; selecting a subset of the calibration data items that have a calibration value within a range of the test output value; and adjusting the test output value based on the membership in the group of the selected subset of calibration data items, wherein the adjusted test output value reflects an adjusted predictive probability for the computer model of membership in the group.