Process capability is reflected on four major factors such as materials, equipments. skill of operators, and methods. The status of the process is typically represented by the mean value 〔$mu$〕as a central tendancy, and the variance 〔$sigma$$^2$〕 as a magnitude of dispersion. This paper analyzes the process capability by the experiment of chips is accounted on a population from the process. So, this paper analyzes the next four cases : (1) When the process distribution is changed from N[$mu$$_1$, $sigma$$^2$〕to N〔$mu$$_2$, $sigma$$^2$〕. (2) When the process distribution is changed from N[$mu$, $sigma$$_1$$^2$] to N[$mu$, $sigma$$_2$$^2$]. (3) When the population is compounded by the different two distributions of N〔$mu$$_1$, $sigma$$^2$〕and N〔$mu$$_2$, $sigma$$^2$〕. (4) When the population is compounded by the different two distributions of N〔$mu$, $sigma$$_1$$^2$〕 and N[$mu$$sigma$$_2$$^2$].