Evaluation of the Calibration of Outside Micrometers by Statistical Repeatability Analysis

Abstract

The study presented in the article focuses on the application of an intermediate accuracy test in a calibration laboratory to assess repeatability among authorized technical personnel performing calibration services in the length range. Technology watch was used to identify relevant, emerging and declining trends in repeatability assessment. To carry out the assessment, the procedure DI-005 established by the Spanish Metrology Centre (CEM) for the calibration of two-contact outside micrometers was followed. Hypothesis tests were applied to estimate the variance ratio and the differences of the population means, ensuring homogeneity of variance, normality (using the Shapiro-Wilk test) and the sample size necessary to use the t-student test. The results obtained in the research showed that the p-values were greater than the 5% significance level, and that the confidence interval estimation for the limits included zero, indicating equality of population means. This demonstrated the existence of repeatability among authorized technical personnel, confirming the reliability of the measurements and the ability to issue calibration certificates.