The Range or R-Chart is used together with the X-bar chart to evaluate process variation. The R chart plots the difference between the minimum and maximum value in each subgroup in time order. The R control chart is appropriate for assessing within subgroup variation when the size of the subgroups is between two (2) and eight (8). The centerline for the R chart is the average of all ranges. The control limits are set at a distance of three standard deviations above and below the center line.
How do I make an R-Chart with TRENDABLE for Data Analysis?