Dear all,

I would like to drop the following:

Our production consists of a a coating process with a roll (batch) as output (ready product). From each produced roll several operators take a sample and count the number of defects (like pinholes or scratches in the coated film). Now, I would like to see if there is a trend regarding the operator that counts the defects. I sorted the inspection results by specification (other layer thickness or other substrate, these things might influence the defect count). It might be obvious that not every operator counts the same amount of samples.

Is it OK if I make U-charts with the operator as subgroup?

Kind regards,

Patric Wessels
Dejima OF
The Netherlands

Yes, a u-chart by operator will work. What you have is an operator sequence rather than a time sequence. So you will want to probably have a bar for each operator, a horizontal average line, and u chart control limits to see if any operator is three standard deviations away from the average. I have attached an example of this sort of chart.

Ok, I just wanted to be sure. Thanks a lot Steve.

best regards, Patric

Mr. Prevette,

I was looking at your example and it appears that some of your data is pulled from another excel sheet on elsmar that I cannot locate. Can you also post that worksheet so I may follow the math so to speak?

Actually, it linked to another spreadsheet on my computer.

Let me post a current example, though I have changed the names of the organizations to protect the innocent (and guilty).