To add value means that three things have occurred.

The process step has changed the form or function of a product or service
The customer is willing to pay for the change
The step is performed correctly the first time.

Any time in the process where value is not added is waste, also known as non-value adding.

There is no use for a non-value adding step, but it is essential that you can see it, reduce it, or completely eliminate it.

The np chart is used when the data can only be whole numbers, as in counting, it is known discrete data (also known as attribute data). Every item in the sample is evaluated for only the number of defects, flaws, or occurrences, etc.

The np chart is used with a fixed sample size where you are counting the number of defectives in the sample. If you remember, the difference between a defect and a defective is this. A defect can be found on an otherwise acceptable product; whereas, a defective means that the whole item is unacceptable.

Ordinal is data that is arranged in order.

You might use the ordinal scale using numbers or symbols to rank order – by importance, by strength, by severity, etc. The intervals are unspecified (e.g., months of the year)

The p chart is used when the data can only be whole numbers, as in counting, it is known as discrete (also known as attribute data). Every item in the sample is evaluated for only the number of defects, flaws, or occurrences, etc.

The p chart is used with a varying sample size where you are counting the number of defectives in the sample. If you remember, the difference between a defect and a defective is this.

Named after the Italian economist Vilfedo Pareto, the Pareto chart is a bar graph used to make visible the vital few vs. the trivial many. Vilfedo recognized that 80% of the wealth in Europe was controlled by 20% of the people. This phenomena in is prevalent in many areas of our lives. In six sigma, there are 20% of the tools that you will use 80% of the time. Think of your tool box at home. Probably 80% of the tools you rarely use. 20% of the tools you use all of the time.

Dr. W. Edwards Deming used a four step process, which is more of a cycle – – PLAN, DO, CHECK, ACT for process improvement. The idea in the PLAN step is to define the process to improve. The DO step is implementing the plan and measuring its performance. The team then takes those measurements to assess whether they are getting the desired results. This is known as the CHECK step. The ACT step follows. The team decides on changes that need to be made to improve the process; then, the whole cycle starts again.

The Poisson distribution is a discrete distribution. The Poisson distribution is quite useful when you want to estimate the probabilities of events that occur randomly in some unit of measure (e.g., the number of traffic accidents at a particular intersection per month).

A way to remember when the Poisson distribution might be useful is when you hear or see the word ‘PER’. Examples of seeing or hearing the word ‘PER’:

A pert chart is used to show activities that are in parallel and/or in series. It will show the most likely times, the most pessimistic times, and the most likely times for the completion of projects. Also known as activity network diagram, arrow diagram, and critical path method.

Pre-control is a control charting methodology that uses specification limits instead of statistically-derived control limits to determine process capability over time.

Pre-control charting is useful in initial process setup to get a rough idea of process capability, but this author doesn’t recommend its use because it is not statistical process control. Pre-control charting does not use continuous data found upstream in the process which is more in alignment with prevention thinking.

Ppk (process performance index) incorporates an estimate of the ‘long-term process standard deviation’ which is standard deviation as we all know it. This includes both the within and between estimates of variation which is usually greater so it reduces the estimate of capability. Ppk is a measurement of how close the center (the mean) is to either the upper spec. or the lower spec. It is generally accepted that you want to have at least six standard deviations between the mean and the nearest specification limit. Ppk however is not measured in single standard deviation units. Instead, it is measured in three sigma sets. For example, if Ppk = 2, there would be six standard deviations between the center of the process (the mean) and the nearest specification limit. Remember the difference between population and sample. If we are measuring a population, we would be looking at sigma units. If we are using Ppk to evaluate a sample set, instead of ‘sigma’, we would be looking at ‘standard deviations.’