XMR charts look at the process rather than the output to determine variation and subsequent action. They postulate that all systems are flawed and accordingly routine variations are common place and don't necessarily reflect an output that needs correctionable action. Given that management is a resource allocation issue, XMR suggests that management can be over reacting to variation and thus allocating resources that don't need to be allocated to correct variations which are largely process based. All processes produce "Noise" and "signals". Action needs to be taken on the "Signals" not the "Noise". Variation within the Upper and Lower control limits could largely be considered noise and just a normal part of process variation. Outputs outside these parameters need attention.