Capability Plot in Excel
One of Six Charts Created Using QI Macros Capability Suite
Create the Same Charts as Minitab's Capability Sixpack™ for a Fraction of the Cost
The Capability Plot is one of six charts created by QI Macros Capability Suite.
A capability plot is just another way to visualize the capability of a process. Below is an explanation of what the 3 lines represent.
Specification: The end points of the specification line are the Upper and Lower Spec Limits.
Within: equals the Standard Deviation of SUBGROUPS - (Rbar/d2 or Sbar/c4).
Overall: equals the Standard Deviation of ALL DATA.
Compare the Specification Line to either of the other two standard deviations
If the Within or Overall lines are wider than the specification line, it means you have data points falling outside of the Spec Limits and therefore your process is NOT capable.
Compare the Within and Overall lines to each other
The two lines should be about the same if the process is stable. Big differences mean an unstable process.
Capable and Stable
Capable, but NOT Stable
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