Cumulative Sum (CUSUM) charts can detect small process changes more quickly than Shewhart control charts, and estimate the changing points easily. Because of these advantages, it is said that CUSUM charts are effective tools to use for process adjustments. However, the current adjustment form is empirical. And it is difficult to say that the form makes enough use on the characteristics of CUSUM charts. The purpose of this paper is to propose the new adjustment from of CUSUM charts in process adjustment. The efficiency of the adjustment is defined as the expected value of the squares of a difference between the true change of mean and the amount of the adjustment. And the adjustment form that minimize the expected value is presented. Proposed from can be designed by having the prior distribution of the process mean and knowing the data size in order to obtain the amount of the adjustment. And it is seen that the proposed from is more effective than the current form.

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In this paper, a preventive maintenance model which generalize Barlow, Glasser and Morse's models respectively are constructed, and the optimal inspection period for the model are obtained. Barlow [1] proposed policy I and policy II for two types of preventive maintenance model in 1960, and afterward Makabe and Morimura [3] modified policy II and called it policy III. Model treated in this paper concerns with policy I ; while in Barlow's model of policy I, optimal preventive maintenance policy which maximizes limiting effeciency is obtained, in this paper policy which maximizes total revenue is discussed.

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