An apparatus for calculating a correlation between annotations includes a first obtaining unit configured to provide an annotator with a first data group capable of being evaluated to determine whether or not to attach annotations thereto, and obtaining a plurality of first confidence levels indicating certainty of the annotations in the first data group, the annotator outputting confidence levels indicating certainty of annotations to be attached to data when the data is given; a second obtaining unit configured to provide the annotator with a second data group used to calculate a correlation between the plurality of annotations, and thereby obtaining a plurality of second confidence levels indicating the certainty of the annotations in the second data group; and a computing unit configured to compute an estimated value of the correlation between the plurality of annotations based on the plurality of first and second confidence levels.