Abstract: The purposes of this paper are twofold. First, to introducea covariance decomposition of the mean probability score in decisiontheory (abbreviated as CDMPS). Secondly, to explore the relationbetween the CDMPS and TSD. Two experiments have been madeaccording to the confidence rating method of TSD. The results of theexperiments proved: (a) The CDMPS can discriminate a person's abilityof judgement from his or her attitude when a decision is made. (b)TheCDMPS has the same effect as the TSD in dealing with sensory eventssuch as the sensation of weight.

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