The Pareto rule, also known as the 80-20 rule or the law of vital few, says that approximately 80 percent of the defects are due to 20 percent of the causes. It is important as it can identify 20 percent vital causes whose elimination annihilates 80 percent of the defects. The qcc package contains the function pareto.chart, which helps in generating the Pareto chart. We will give a simple illustration of this chart.
The Pareto chart is a display of the cause frequencies along two axes. Suppose that we have 10 causes C1 to C10 that have occurred with defect counts 5, 23, 7, 41, 19, 4, 3, 4, 2, and 1. Causes 2, 4, and 5 have high frequencies (dominating?) and other causes look a bit feeble. Now, let us sort these causes by decreasing the order and obtain their cumulative frequencies. We will also obtain their cumulative percentages:
> Cause_Freq <- c(5, 23, 7, 41, 19, 4, 3, 4, 2, 1)
> names(Cause_Freq) <- paste("C",1:10,sep="")
> Cause_Freq_Dec <- sort(Cause_Freq...