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; 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.