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Capability Indices/Process Capability
50 Percent Sampling Savings With Sequential Test Method
Using Wald's sequential test method for process capability decisions can result in 50 percent sampling savings. Sequential testing can also be automated, enhanced and extended to the binomial, Poisson and reliability test areas.
Calculate Capability Indices with Only One Specification
The example of a plastic pellet manufacturer shows how to apply process capability to a process with only one specification.
Calculating Process Efficiency in Transactional Projects
Principles of Lean manufacturing are applicable to any business process. This article reviews some of the common problems seen in transactional projects and outlines an example where simple graphical methods are used to interpret cycle time data.
Capability and Performance
Some practitioners are confused about the differences between Capability and Performance indices. This article explains the uses of both.
Competently Use Capability Analysis
Process capability indicates how well a process is able to perform its specified purpose. iSixSigma has gathered its best resources on the subject in one convenient location.
Cp, Cpk, Pp and Ppk: Know How and When to Use Them
The difference between Cp and Pp, as well as between Cpk and Ppk, results from the method of calculating standard deviation. Cp and Cpk consider the deviation mean within rational subgroups, while Pp and Ppk set the deviation based on studied data.
Finding the Sigma Level of Customer Complaints
Although customer survey data is often used to determine the degree of customer satisfaction, it is worthwhile to consider recorded complaints data in order to calculate the number of actual complainers and the number of possible complainers.
Getting the Most out of a Capability Analysis
Many articles describe the difference between the process capability indices simply: one is short term, one is long term. Moving beyond such a description, this article focuses on the untapped power of capability analysis and shows you how to use them to your advantage.
How to Avoid Common Mistakes When Measuring Performance
Quality indices Cpk, DPMO and first pass yield are prevalent criteria for gauging the performance of products and processes. These indices, however, often are interpreted wrongly and used without taking into account the conditions of application.
How to Calculate Process Sigma
Calculating your process sigma can be accomplished in 5 simple steps: Define your opportunities, define your defects, measure your opportunities and defects, calculate your yield, look-up process sigma. This article includes all the tools you need.
How to Explain and Understand Process Capability
Have you ever tried to explain the concept of process capability to someone and received a blank stare in return? Try using an analogy of driving different vehicle types on a highway under construction to explain the topic more easily.
Overcoming Capacity Constraints with Optimization Modeling
"Speed is survival." That could be called the mantra for all manufacturing and service organizations in todays uncertain and continuously changing global economy.
Process Capability – Surface Finish Example: Part 2
In Part 2 we look at failure rates and material conditions for a surface finish example.
Process Capability – The Basics: Part 1
In Part 1, we explore the concept of process capability, including how to calculate it and what to do with non-normal data.
Process Capability (Cp, Cpk) and Process Performance (Pp, Ppk) – What is the Difference?
Six Sigma process performance is reported in terms of Sigma. But the statistical measurements of Cp, Cpk, Pp, and Ppk may provide more insight into the process. Learn the definitions, interpretations and calculations for Cp, Cpk, Pp and Ppk.
Process Capability Calculations with Non-Normal Data
Data that is not distributed normally can be analyzed more effectively by: 1) dividing data into subsets according to business subprocesses, 2) mathematically transforming data and specification limits and 3) turning continuous data into discrete data.
Process Entitlement Analysis: Using This Novel Approach
Many efforts to analyze a poor project selection process fall short of their overall objective. Process entitlement analysis is a concept that provides an effective and robust process to conduct a total improvement opportunity assessment.
Resolving Common Issues with Performance Indices
To resolve measurement issues, practitioners need a common measurement for making process stability and capability assessments at all levels of a business, independent of who is making the assessment something beyond Cp, Cpk, Pp and Ppk.
Table of the Standard Normal (z) Distribution
Z score is a measure of the distance in standard deviations of a sample from the mean. It is calculated as (X - X bar) / sigma. The table of z distribution is shown here.
The Douglass Index Can Keep Good Data from Going to Waste
The Douglass Index allows practitioners to convert data with poor-to-marginal repeatability and reproducibility to a marginal process capability (Cp) level.
Understanding First Time and Rolled Throughput Yields
There are two ways to calculate the yield from a process: first time and rolled throughput. Look hard at the way you calculate yield and how you use the results.
Using OEE Metrics for All Process Steps
Production time can be consumed by various planned and unplanned activities. Formally detailing these times can yield valuable insight into why so many hours must be consumed to generate a given amount of work.
Using Weighted-DPMO to Calculate an Overall Sigma Level
It can be difficult to assess an overall sigma level because some critical processes are more important than others. One approach is to weight each of the critical processes when calculating overall sigma level.
Zero Defects: What Does It Achieve? What Does It Mean?
The use of slogans such as "zero defects" to spur quality can be counterproductive, detracting attention from the tried-and-true tools and culture associated with successful Six Sigma programs.
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