Comparison of individual charts to monitor peroxide index of olive oil

摘要

The peroxide index is an important variable measured in order to assess the quality of olive oil. However, the normality assumption of its distribution fails the test in this case study. The control limits of individual chart for peroxide index of virgin olive oil are obtained considering the average and also the median moving range. A non-parametric method based on empirical quantiles, quite robust against deviations from normality, is also applied with the bootstrap procedure to estimate control limits for the individual chart. The conclusions obtained with these approaches are relatively different.