LSSGB: What type of control chart should the team recommend for the following scenario?

A team of six sigma has reached the control stage of DMAIC. They have successfully reduced fabric critical stains from 73 to 1 per fabric roll. Now what type of control chart should the team recommend?

OPTIONS

• A control chart based on the normal distribution such as the X-bar chart
• A control chart based on the Poisson distribution such as the u chart
• A p chart based on the binomial distribution
• An np chart based on the binomial distribution

Answer

A control chart based on the Poisson distribution such as the u chart

EXPLANATION

All four answers refer to valid control charts, but only answer b recognizes the Poisson nature of the improvement achieved. Critical stains are defect counts which are descriptive of the Poisson distribution. All other chart options are improper applications.