Statistics for Six Sigma Made Easy

8.2. VARIABLES

There are many factors that can affect sampling. Here are a few to make you more aware of the complexity and difficulty of getting good data.

Sometimes an inspector "adjusts" data, truly believing that the adjustment gives a truer picture of the actual process. Here's an example.

I was watching an inspector who was inspecting product on a high-speed production line. On a regular basis, a random product was picked from the conveyor line and placed onto a fixture, which had several electronic gauges that took key measurements. These measurements were displayed on a computer screen and then automatically sent to the quality database, unless the inspector overrode the sending of the data. The override was intended only if the inspector ...