Histogram in Excel with Cp, Cpk
Are You Tired of Trying to Create Histograms in Excel?
- Does the Data Analysis Toolpak take too long and require too many steps?
- Is it difficult to show specification limits or the normal curve?
- Is it too hard to calculate process capability statistics? Defect rates? Sigma?
Its easy to draw histograms with the QI Macros SPC Software for Excel.
What is a Histogram?
Histograms show the spread, or dispersion, of variable data. The customer's upper specification (USL) and lower specification limits (LSL) determine how well the process delivers on customer requirements.
What is Cool about the QI Macros Histogram?
Just select your data and select Histogram with Cp Cpk from the QI Macros menu. The macro will prompt you for spec limits and will create a histogram and calculate process capability metrics for you. All of the calculations can be viewed in the data sheet created by the macro. You can see how the spec limits impact Cp Cpk by changing them in the data sheet and you can adjust bin intervals and the approximate number of bars.
- Process Capability Analysis Quick Reference Card (PDF, 172 KB)
Why Use a Histogram?
Use a histogram to determine the distribution of measurable data and the capability (i.e., the level of performance the customers can consistently expect) of the process.
In the chart above, there are measurements below the LSL and above the USL which means that the process doesn't always deliver on the customer's requirements.