FMEA – Detectability number is confusing

If the team is struggling with the concept of the worse the detectability the lower the score, then don’t depend them to assign the values. Let them assign the detectability using the subjective approach (more than once per day to once every 5-100 years)or the the probability (>20% to 20% to 20% to

My bad. I was multi-tasking during the response and addressed the wrong scale. For your team you could just ask the to determine the detectability from the following scale:
10. Defect Undetectable
9. Units sporadically checked for defects
8. Units systematically sampled and inspected
7. All units manually inspected
6. Mistake-proofing modifications after inspection
5. SPC and manual inspection
4. SPC w/immediate reaction to out-of-control
conditions
3. SPC w/100% inspection surrounding out-of-control
conditions
2. 100% automatic inspections
1. Defect is obvious and can be kept from reaching
customer.Let them agree to characteristic on the right and do not even show them the number associated with it. Let them review the RPN when you are done, and it should make sense to them.

I concur with Alastair. I would rather the team try and understand the logic of the higher number for the lower detectability.

I meant to add all Criteria:

Effect
Criteria: Severity of Effect
Ranking

Hazardous — without warning
May endanger consumer.  Very high severity ranking when a potential failure mode affects fitness for use and efficacy of product and/or noncompliance with government regulation.  Failure will occur without warning.
10

Hazardous — with warning
May endanger consumer.  Very high severity ranking when a potential failure mode affects fitness for use and efficacy of product and/or noncompliance with government regulation.  Failure will occur without warning.
9

Very High
Major impact upon product flow and/or probability of acceptance.  100% of product may have to be scrapped.  Product is nonfunctional.  Consumer very dissatisfied.
8

High
Minor impact upon product flow and/or probability of acceptance.  A portion of the product (<100%) may have to be scrapped.  Product is functional, but at a reduced level (e.g., cosmetic defects).  Consumer dissatisfied.
7

Moderate
Minor impact upon product flow and/or probability of acceptance.  A portion of the product (<100%) may have to be scrapped.  Product is functional, but at a reduced level (e.g., cosmetic defects).  Consumer experiences discomfort.
6

Low
Minor impact upon product flow.  100% of the product may have to be reworked.  Product is functional, but at a reduced level.  Consumer experiences some dissatisfaction.
5

Very Low
Minor impact upon product flow.  The product may have to be sorted and a portion (<100%) reworked.  Cosmetic defects noticed by most consumers.
4

Minor
Minor impact upon product flow.  A portion of the product (<100%) may have to be reworked.  Cosmetic defects noticed by consumers.
3

Very Minor
Minor impact upon product flow.  A portion of the product (<100%) may have to be reworked.  Cosmetic defects noticed by discriminating consumers.
2

None
No effect
1

Probability of Failure
OCCURRENCE (Possible Failure Rates)
Ppk
Ranking

Very High
> 1 in 2
< 0.33
10

1 in 3
>0.33
9

High
1 in 8
>0.51
8

1 in 20
>0.67
7

Moderate
1 in 80
>0.83
6

1 in 400
>1.00
5

1 in 2,000
>1.17
4

Low
1 in 15,000
>1.33
3

Very Low
1 in 150,000
>1.50
2

Remote
< 1 in 1,500,000
>1.67
1

Detection
Criteria: Likelihood the existence of a defect will be detected by process controls before next or subsequent process, or before product leaves the processing location.
Ranking

Almost Impossibe
No known control(s) available to detect failure mode.
10

Very Remote
Very remote likelihood current control(s) will detect failure mode.
9

Remote
Remote likelihood current control(s) will detect failure mode.
8

Very Low
Very low likelihood current control(s) will detect failure mode.
7

Low
Low likelihood current control(s) will detect failure mode.
6

Moderate
Moderate likelihood current control(s) will detect failure mode
5

Moderately High
Moderately high likelihood current control(s) will detect failure mode
4

High
High likelihood current control(s) will detect failure mode
3

Very High
Very high likelihood current control(s) will detect failure mode
2

Almost Certain
Current control(s) almost certain to detect failure mode.  Reliable detection controls are known with similar processes.
1
 
 

Chad:It’s always strange to ask a team to find out how many defects are NOT detected. It’s like asking how many people have successfully embezzled money from the company.Your list is a nice scale for detectability. We usually modify the scale for the particular project using the worst case (10) and the best case (1) to get a good range. We can sometimes define the rating using scenarios like;”If you processed 1,000 claims each week and you somehow knew 100 had missing information, how many times would someone pick them up at this process step? Would it be 1, 3, 10, 30, 100?”We can refine some of the numbers by comparing two similar ratings by asking,”Of these two failure modes, which is likely to be detected better (or worse)?”You can sometimes get some information using the number of defects reported (detected) at various process steps.Cheers, Alastair

Wow, a lot of talk about something simple. The rating represents risk – the higher the rating the greater the risk.

Alastair, I put together these detection criteria based on several sources and molded into one that “Works for Me”. I agree with what you say, but I had to determine what the team I was dealing with regulary could comprehend.
Have a reference to look at, not only cleared confusion about the rating, but alson created thought around the number that was assigned and I found it very helpful
 

I didn’t say I developed these, what I said “I put together these detection criteria based on several sources and molded into one that “Works for Me””
Several Sources being Key. Plegiarized, I guess, Or maybe just resourceful…….Yes Some came from AIAG,
Some of it came from Six Sigma Academy (2002 GOAL/QPC)
Some of it came from Lean Six Sigma by Michael L George Pg 190-191
And other confidential and proprietory to TYCO International LTD training documents for week #1 GB
Good Day  

You did a lot of work to come up with something that was already in
AIAG. Your detection is no better and no more helpful than theirs.

I was so resisting the urge to post that same response.

It seems to me many of the posts in this forum have unstated assumptions about the type of FMEA. 
I’m a design engieer for implantable medical devices (high risk).  We use FMEA on every product.  We have team members from engineering, marketing, clinical/nursing and regulatory – and the team gets confused about this topic almost every time.  I have been working to define Detectability based on the type of FMEA:
Design FMEA – how detectable (thing preventable) is the Cause of this failure (line on the FMEA table).  That is, if the cause is a poor weld, and welding is a new process for us, what will we do (mitigate) during the design and development to prevent this.
Process FMEA – how detectable (think preventable) is this Manufacturing Cause of this failure (line on the FMEA table).  That is, if two parts are bonded during assembly with the wrong aligment to each other, what can be done during assembly to mitigate this?  Mitigation could be create an alignment fixture or request a design change so that the parts can not be assembled in the wrong orientation.
Application FMEA (User FMEA) – how dectable is an in-use problem by the user in his work environment, such that he can recognize the problem before it happens (or the equipment self detects and gives the user warning with enough time to correct the situation).  For us, this is a good for evaluating risk when planning to allow use of our existing products in new user environments.  Example – using a general IV Pump on newborn babies.  The maximum pumping rate can be so high that a days worth of drug is administered in 1 hour – killing the patient.  A mitigation might be a designed in warning, the pump feeds back the settings and requests user confirmation because of the high pumping rate request.  A product acceptable in one user-environment can be risky when used in another environment.