UCL and LCL

[vizhi]

Hi...
What is the explanation of UCL and LCL?
How to calculate?

[rekha]

UCL(UPPER CONTROL LIMIT),LCL(LOWER CONTROL LIMIT) is calculated from process data to determine what the process considers the area where it will vary inside if there are only common causes happening. The calculation is often automatically done by software and the formula's used depend on the type of control chart.

Sorry I don't know the formula.

[nirmala]

Hi...
LCL and UCL are actually pretty easy to calculate. They are 3 standard deviations from the mean. So you need the mean, first.
Here are the formulas
Mean
Sum(I=1 to n, Metric[I]) / Sum(I=1 to n, size of Item[I])

Upper Control Limit (UCL)
Mean + 3*Sqrt( Mean / Average item size)

Lower Control Limit (LCL)
Mean - 3*Sqrt( Mean / Maximum item size)

LCL is never allowed to be less than zero
“Maximum item size” makes LCL more sensitive