1. An apparatus comprising: a target data acquiring section operable to acquire target data serving as an examination target, the target data output by a plurality of sensors; a calculating section operable to calculate, for each of a plurality of sensor groups that each include at least two sensors among the plurality of sensors, a degree of outlierness of the target data relative to a reference data distribution of output from the sensor group; and an estimating section operable to estimate a sensor among the plurality of sensors to be a source of outlierness, based on a calculation result of the calculating section.