Adjusted Control Limits for U Charts

Abstract: U charts are used for count data following the Poisson distribution.  However, the U chart has symmetrical control limits when the Poisson distribution is nonsymmetrical.  As a result, the upper control limit can have a rate of false detection as high as 1 in 11.5 points plotted.  This can result in wasted resources investigating […]

Adjusted Control Limits for U Charts Read More »