(1) To estimate relationships (and constant terms) for use in a forecasting model. (See also fit.) Some software programs erroneously use the term forecast to mean calibrate. (2) To assess the extent to which estimated probabilities agree with actual probabilities. In that case, calibration curves plot the predicted probability on the x-axis and the actual probability on the y-axis.  A probability assessor is perfectly calibrated when the events or forecasts assigned a probability of X occur X percent of the time for all categories of probabilities assessed.