100% Inspection - 80% Accurate - Quote from Juran (?)

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E

energy

#11
Me too!

Originally posted by D.Scott
I sure don't want to argue with the anybody on this issue, especially Juran. IMHO I think the "100% inspection is only 80% effective" statement is a cop out used way too much to justify a poor inspection process.
I am not a statistician but the logic that the chance of a second inspector finding a single defect would be lower than the first inspector doesn't seem to make sense. The chance of finding the defect would INCREASE for the entire process (using mechanical inspection to eliminate the "he thought - she thought" sceanario).
Dave
My sentiments exactly! As an Inspector-Full Time for 14 years, and still am occasionally, I find the assumption that Inspectors are generally prone to not performing as they should, crap! I wonder if the great master Juran ever spent time doing this type of work. Maybe when this study was done, he was standing behind the Inspectors, no doubt looking down on them, with his clipboard pacing back and forth. :))
When I had an assignment, it made no difference to me if it was looked at prior to my inspection. Most serious Inspectors assume that there is something not right and will not let it go until they are completely satisfied that it meets all the requirements. We are a paranoid group. I have been following this thread and this 80-20 rule, another buzz word I might add, that is used for just about anything these days. Not wanting to ruffle anyone's feathers, nor offend the Juran aficionados, I was waiting to see a post that questioned what appears to be acceptance by the majority that Inspectors are lazy, or worst yet, incompetent. Thanks for a breath of fresh air. Just because it's printed and preached doesn't always make it so! :smokin:
 
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Marc

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#12
I think Mr. Scott's point is a good one (and I expected energy to weigh in ;) God bless his conservative soul). I can't disagree. I know they teach this with the 'find all the F's in this paragraph dealie' (one version of which is posted here somewhere. Someone - I forget who - probably Eileen {she is a wonderful contributor here} - uploaded it) which does show - and I believe - inspectors do miss things from time to time. I'm less sure about the double inspection aspect of the theory.

It seems to me most important would be the inspection. As Mr. Scott pointed out it is hard to miss whether a refrigerator got the red paint or not. Another issue is how long and how many. If you have 0.5 minute to inspect a circuit card with 10 critical features to be inspected, and you have to do that for 2 hours streight, you start increasing the odds of inspectors missing a defect.

I have worked in several places that would only allow an inspector to 'work' for 2 hours and after a break would have to inspect a different part. These were in Mil houses doing circuit card inspections. The rational was that an inspector can 'get used to' the part and after a while not see some defects.

In another thread someone asked: "...how much receiving inspection should we use?..." I haven't read the whole thing yet (I saw it in my e-mail and have yet to get to that thread) - so I might be missing something - but it depends upon the part, it's criticality, etc. There is no single answer in a forum setting such as this unless a lot of info is posted for people to have a reasonable understanding of the situation as a whole. I mention this because I would never hesitate to use a visual inspection when it is appropriate - which is what you have to determine. If your NC-CA system shows parts are getting by a visual inspection, regardless of the "80-20 Rule", you investigate the problem. for example: Did this just start happening (i.e.: was visual inspection working before but is not now)?

You may have to give inspectors more time or more frequent breaks. It may be the best way is a poka yoke. But the bottom line is visual inspection is not worthless. You have to look at the inspection and the context it is in.

As a last comment, I have seen non-visual inspections fail. In one scenario there was a simple continuity check. When we looked at the situation, it was mostly a matter of boredom and part the human brain. After a while the inspector 'thought' s/he heard the buzzer when in fact it had not buzzed. The inspection was simple and it would be too expensive to break up the line and insert an auto test machine. We slowed down the number of inspections per person per hour and added an inspector and the problem dropped dramatically (not entirely, but to an 'acceptable' level). Final test was an automated test fixture which 'exercised' the CCA which precluded any earlier inspection failures from leaving the plant.
 
E

energy

#13
Deming, too?

Originally posted by Kevin Mader
Dr. Deming offered this in regards 200% inspection: Inspector 1 thinks inspector 2 will catch the defect while inspector 2 thinks inspector 1 will catch it. Net result: nobody inspecting.
Kevin
Hi, Me Again:eek:

I agree with the premise that Inspectors do get tired. The degree of fatigue is proportional to the complexity. But the statement that an Inspector won’t inspect if he knows another Inspector has or will inspect the same thing, amazes me. This isn’t fatigue, boys. This is outright fraud.
Having shown my righteous indignation of suggesting that Inspectors may be not inspecting, there has to be reason for double inspection. I used to be a “double inspector” working on an aircraft assembly line. Two inspectors would begin inspecting flight control cables, turn buckles, control rods, etc., from opposite end of the aircraft. The lead seal was attached to all adjustable linkages that allowed for two Inspectors to each apply their personalized stamp. You would eventually pass each during the process. Does that mean I would stop inspecting because I saw his stamp on the seal? I would just stamp it? Give me a break! Then there was third Inspector who verified that all the seals contained a double stamp impression and that everything looked good. He/she also had overview authority and experience in this area. So, there is reason to double, triple check things. Is it fatigue? I agree. If it’s because they didn’t inspect it all, absolutely unbelievable:ko: :smokin:
 

Kevin Mader

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#14
3 inspectors inspecting the same thing = .8 x .8 x .8= .51 or 51%

I see that I may be swimming in the deep end alone here, but I'll take my chances.

p.s. energy, you would still jump in an save me if I went under, wouldn't you? :eek:

Kevin
 
E

energy

#15
Of course!

Originally posted by Kevin Mader
p.s. energy, you would still jump in an save me if I went under, wouldn't you? :eek:
Kevin
Kevin,

Anything for a fellow Connecticut Quality Dude! You're just quoting what's published. :)) You don't believe everything you read. CT Yankees are the worst:rolleyes: :smokin:
 
#16
Two inspectors = no inspections

Energy,

It might not be a case of fraud; it may be a case of too much faith in the other person. If I know you are a good inspector, I might not work as hard as if I had little faith. Is this fraud? Perhaps.

In another situation: A video duplication discovered they mislabeled a bunch of videotapes. Because of records, they knew exactly how many were nonconforming. They sent the inspectors out to the warehouse to find them. On the first pass they found all but a dozen. The second pass lowered the number of missing tapes to 5. The third pass found two more. The fourth and fifth passes could not find any. “There are none left. We know this.” The inspectors claimed. A new batch of inspectors was sent in to find the remaining 5 tapes (Not a typo). They returned saying they could only find three (which was all that remained). The first group of inspectors couldn’t find the mislabeled tapes because they thought they found them all. Consciously, or not, they quit inspecting.

Not the same thing, but the same result.

Dave B (the other Dave)
 

Kevin Mader

One of THE Original Covers!
Staff member
Admin
#18
Heres more food for thought:

Recently on the news, I heard that after recounting the votes, Gore did win Florida.

Gore wins, then loses on a complete count, then wins again (sort of) on a recount.


Sample results - 100% inspection results - 100% inspection results.

What result do you believe in?
 
#20
Is 100% Inspection 100% Failure?

Energy, and Kevin

You know it almost sounds like we are saying exactly the same thing differently. My concluion is that in everything from videotapes to elections, we can't count on 100% counting.

Dave B (the other Dave):))
 
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