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 〔μ〕as a central tendancy, and the variance 〔σ²〕 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[μ¹, σ²〕to N〔μ₂,σ² 〕. (2) When the process distribution is changed from N[μ₂,σ² ] to N[,μ₂,σ² ]. (3) When the population is compounded by the different two distributions of N〔μ₁,σ² 〕and N〔μ ,σ½ 〕. (4) When the population is compounded by the different two distributions of N〔μ ,σ½ 〕 and N[μ,σ].