1. An apparatus comprising: an obtaining unit configured to obtain first image data obtained by reading, performed by a reading unit, a chart on which an image has not been formed by an image forming unit and second image data obtained by reading, performed by the reading unit, a chart formed by the image forming unit; and an estimation unit configured to change the second image data using the first image data and estimate a cause of an abnormality that has occurred in the image forming unit from a feature amount obtained by analyzing the changed second image data.