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  Statistical Techniques and 6 Sigma
  p charts

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Author Topic:   p charts
Dawn
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Posts: 245
From:St. Marys, PA
Registered: Sep 98

posted 14 January 1999 11:13 AM     Click Here to See the Profile for Dawn   Click Here to Email Dawn     Edit/Delete Message   Reply w/Quote
I have been told in the area where I reside NOBODY uses these charts for any benefits. I am only starting to look into attribute control charting and I think there would be alot of benefit in using them. In my opinion it would help awareness issues immensely.Can anyone give me some feedback?

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Don Winton
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Posts: 498
From:Tullahoma, TN
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posted 14 January 1999 12:35 PM     Click Here to See the Profile for Don Winton   Click Here to Email Don Winton     Edit/Delete Message   Reply w/Quote
Dawn,

What I like about p charts is they give a snapshot of your process control, process capability AND your process yield in one chart. I have used these successfully in many applications. One word of caution: Any chart, regardless of type, is only useful if used as a continuous improvement tool. Too often, however, they are just used as wallpaper, IMHO.

quote:
I have been told in the area where I reside NOBODY uses these charts for any benefits.

I believe the reason that attribute charts get a bum rap is becuase they are not as straightforward to calculate and interpret as the typical Xbar-R charts. IMHO, if NOBODY is using them, that may be because they do not understand them.

quote:
In my opinion it would help awareness issues immensely.

Agreed. Go for it.

Regards,
Don

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Batman
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Posts: 111
From:Kane, PA 16735
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posted 14 January 1999 08:04 PM     Click Here to See the Profile for Batman   Click Here to Email Batman     Edit/Delete Message   Reply w/Quote
My experience with P charting has not been good. The first hurdle is that you are charting defects. If there are only one or two of these going on, and there is visible activity to "fix" the process, it should not be a problem. Unfortunately, a couple of years ago we had more than a couple of these charts, which the engineers were using in weekly meetings to demonstrate "sameness" in their areas of responsiblity. What was lost on them was the operators reporting the percent defective began to get used to defects being OK, and some took this to other departments after they bid or were transferred. It became a pervasive problem. Our customers do not stand for defects, and we had already set up 100% inspection for these parts to protect the customer. I could get information just as quickly from the inspector's time cards each day.
Prior to QS9000 implementation, I recall two instances where customer auditors found P charts more than 5 months old, and they obviously looked for corrective action. All they saw was 100% inspection.

I can certainly see benefits for utilizing P charts, but I am tentative when someone wants to use one for more than a couple of days or weeks.
BTW, we are high volume component and assembly supplier to Ford, GM, Japan.

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Don Winton
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Posts: 498
From:Tullahoma, TN
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posted 15 January 1999 06:53 PM     Click Here to See the Profile for Don Winton   Click Here to Email Don Winton     Edit/Delete Message   Reply w/Quote
quote:
If there are only one or two of these going on, and there is visible activity to "fix" the process, it should not be a problem.

Agreed. It serves no purpose to maintain a p chart (or any other chart for that matter) without trying to improve upon the current process.

quote:
... which the engineers were using in weekly meetings to demonstrate "sameness" in their areas of responsibility. What was lost on them was the operators reporting the percent defective began to get used to defects being OK...

Goes back to my point about so much wallpaper. There must be positive proaction to attribute charts when they are used else they are useless. Demonstrating ãsamenessä is just plain WRONG and, IMHO, stupid.

Certainly there are acceptable alternatives to attribute charting to continuously improve. I like the attribute chart for the reasons I cited in my first post.

Regards,
Don

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