David, I wrote two visual basic for applications User-Defined functions that calculate Cp and Cpk just like any other formula in Excel. By attaching the visual basic module to a new, blank worksheet and saving this worksheet as your start-up template (see Excel’s online help for detailed instructions), you can have these formula readily available in every new worksheet you make. Capability (Cp, Cpk) and Performance (Pp, PpK) indices are a means of comparing (among other things) if the data is made up of common versus special causes of variation. When a system behaves under common causes the data will be normally distributed. If this is the case then Cp=Pp and Cpk=Ppk (they won’t be exact but very close). Capability (Cp) and performance (Cpk) charts illustrate a process’s ability to meet specifications. Although SPC control charts can reveal whether a process is stable, they do not indicate whether the process is capable of producing acceptable output—and whether it is performing to capability. My customer wants to know if my process is capable of meeting their specifications and is in statistical control. My boss needs the process capability for the monthly report. I would like to track all the Cpk and Ppk values of my processes? My data are not normally distributed; I need a non-normal process capability analysis. See What Process Capability in SPC for Excel.
There are two types of research in statistics such as quantitative and qualitative data analysis. Quantitative data which is used to the measure the values or counts and expressed in numbers and represented through name, symbol or number code. Qualitative data analysis are said to be categorical measurement which are not expressed in terms of numbers, but expressed by means of natural language. This section consists of the list of all qualitative and quantitative data analysis calculators.
The frequency of observation can be calculated in quantitative data. Qualitative data are extremely varied in nature and captures the values which are not natural in numbers. Qualitative data's are not used mostly with inferential statistics because as all the techniques are based on the numerical values.
Cp stands for process capability and Cpk stands for process capability index. Both are used for the measure of a potential capability of a process in short term. The higher the sigma level, the better the process is performing. You can learn how to calculate Cp and Cpk values using this tutorial. Learn to calculate the Process Capability (Cp) and Process Capability Index (Cpk) values using the steps and few examples given here.
Process capability is a technique to find out the measurable property of a process to a specification. Generally, the final solution of the process capability is specified either in the form of calculations or histograms
Process capability index (cpk) is the measure of process capability. It shows how closely a process is able to produce the output to its overall specifications.
USL = Upper Specification Limit, LSL = Lower Specification Limit.
Food served at a restaurant should be between 38°C and 49°C when it is delivered to the customer. The process used to keep the food at the correct temperature has a process standard deviation of 2°C and the mean value for these temperature is 40. What is the process capability of the process?
USL (Upper Specification Limit) =49°C LSL (Lower Specification Limit) =39°C Standard Deviation =2°C Mean = 40
Process Capability & Process Capability Index
|Process Capability :|
|Process Capability||= (49 - 39) / (6 * 2)|
|= 10 / 12|
|Process Capability Index :|
|(USL-mean/ 3*std.Dev)||= (49 - 40) / (3 * 2)|
|(mean-LSL/3*std.Dev)||= (40 - 39) / (3 * 2)|
|Now, find the minimum value.|
|Process Capability Index||= min (Solution 1, Solution 2)|
|= min (1.5 , 0.166)|
Cp and Cpk are used in Six Sigma Quality Methods for analyzing the performance of the process carried out to deliver any product.