Investigation of the Effects of Normal Distribution or Nonnormal of Data on Machine Capability Analysis
Abstractprocesses in the business world have two fundamental disease, including deviation and variability from the average (target). One of the statistical process control graphs used for quantitative variables is to keep the average and the other to control variability. Apart from the normal distribution or nonnormal of quantitative data, the average and variability are controlled or not, and then the capability of process or machine is checked. The desired outcome is in addition to the normal distribution of data, the process is under control and capable. On the other hand, capability analysis is defined as the machine capability analysis when it is performed for the machine, while the process capability analysis takes its name when it is done for the process. In this study, machine capability analysis has been applied. The aim of this article is to investigate the effects of the normal distribution or nonnormal of data on machine capability analysis. For this purpose, data on the lengths measured by surface of the shock absorber body pipe cut by a CNC machine in a company in the automative industry were used. In the study, 50 observations values were used, and the lower specification limit was 124.5 and upper specification limit was 125.5, and the CNC (pipe cutting) machine was sufficient or not. The analysis first started with the implementation of the normality test and the data was not distributed normally. It is concluded that assuming this data, which does not have normal distribution, is normally distributed, and the machine is under control and is also sufficient with the I-MR control charts in the Minitab program. The same analysis was applied with the nonnormal command under the assumption that the data was nor normally distributed, and even in this case the machine was sufficient. In addition, the data that does not have normal distribution has been transformed into normality, and I-MR control charts and machine are under control and also sufficient. According to the findings, the average and specification limits of the values of I-MR control charts are the same and the machine capability results are different. In this study, these similarities and differences were examined comparatively. Let us add it right away; these findings are specific to the machine and cut pipes we take into consideration and should not be generalized.