I recommend adding a table of p values for Ni+1 to the Pareto Plot. This would help in statistically determining which categories in the plot to address. The details and calculations are shown in Quality Progress Nov 2020 issue pages 38-43. The article is 'Critical values for Pareto comparisons remove statistical subjectivity' by Frank Rudisill and Jim O'Connor. The calculations are on page 42. Table 3 on page 43 shows an example containing a p value for Ni+1 which could be added in part or in full to the Pareto Plot.