Bowling Charts - The Red, Yellow, Greena

B bowling charts are a, i think that term's pretty commonly used for. It can be really misleading, with color coating or not. I don't think the human brain is really well attuned to detect trends by looking at a list of numbers. A data point that's below the lower limit tells you the system is changed. And correct things and put performance back where it was rather than letting performance continue to degrade until suddenly it goes yellow or red.