2. The method of claim 1 , wherein: obtaining the plurality of first confidence levels includes obtaining the plurality of first confidence levels by transmitting the first data group to the annotator to determine that the annotations should not be attached to the first data group; and computing the estimated value of the correlation between the plurality of annotations includes computing a plurality of first representative values by executing operations to find a first representative value of each confidence level in the plurality of first confidence levels and compute the estimated value of the correlation using the plurality of first representative values and the plurality of second confidence levels.
2. The method of claim 1 , wherein: obtaining the plurality of first confidence levels includes obtaining the plurality of first confidence levels by transmitting the first data group to the annotator to determine that the annotations should not be attached to the first data group; and computing the estimated value of the correlation between the plurality of annotations includes computing a plurality of first representative values by executing operations to find a first representative value of each confidence level in the plurality of first confidence levels and compute the estimated value of the correlation using the plurality of first representative values and the plurality of second confidence levels. 5. The method of claim 2 , wherein the computing unit computes the estimated value of the correlation using a formula for computation in which the plurality of first representative values are used to correct an expression of dividing a second representative value of a product of the plurality of second confidence levels by a product of a plurality of second representative values, wherein the second representative values are obtained by executing operations to find a third representative value of each confidence level in the plurality of second confidence levels.