<p> In society that change suddenly, citizens need to acquire competency in making decision in everyday and professional situations.  On making decision, they need to rate choices and judgement using probability is needed at that time.  That is, competency of judgement using probability is important as competency of decision making.  Therefore, the purposes of this paper are to: ・ Propose the contents of learning that consider training of competency of judgement using probability in making decision. ・Derive the task based on the contents of learning for revision of teaching probability. The results of this paper are the following three things: ・ From the development of history of probability, there are suggested that a way of mutual understanding of the frequency idea and the subjective idea are important, and citizens need to do judgement using probability  that follow Bayes rule in everyday and professional situations. ・ It is effective that students learn Bayes theorem that is methodology of Bayes rule to train the competency given above. ・ From result of the research on actual conditions in this paper, because the treatment of Bayes theorem is inadequate in the teaching probability currently being used in view of training the competency given above, it is needed that the overall revision to the teaching probability from the Bayes theorem on down from the current.</p>