1. A computer-implemented method for estimating an ability of a worker in a process for integrating work results of multiple workers for the same task, the method comprising: acquiring, for each of one or more tasks, a work result of a preceding-stage worker and a work result of a succeeding-stage worker that works based on the work result of the preceding-stage worker; and estimating multiple parameters of a probability model in which an ability of the succeeding-stage worker conditioned by a quality of the work result of the preceding-stage worker is introduced as a conditioned ability parameter, based on the multiple work results obtained for each of the one or more tasks.