Medical Device FMEA Occurence Rating Scale Justification

[jenna]

Hello,

I work in a medical device company. Recently we've been asked to justify occurence rating scale that we use in our FMEAs and I am at a loss about how to do it. We currently have a 5 point quantitative scale, ranging from 1 out of 100,000 to 1 in 100.

Does anyone have any experiense in justifying their scales? We have plenty of historical data, but I don't really know what to make of it, how to slice and dice it.

Any help is appreciated.

Thanks,
Jenna

[Jim Wynne]

In Reply to Parent Post by jenna

Hello,

I work in a medical device company. Recently we've been asked to justify occurence rating scale that we use in our FMEAs and I am at a loss about how to do it. We currently have a 5 point quantitative scale, ranging from 1 out of 100,000 to 1 in 100.

Does anyone have any experiense in justifying their scales? We have plenty of historical data, but I don't really know what to make of it, how to slice and dice it.

Any help is appreciated.

Thanks,
Jenna

I don't know if there are any specific medical-device requirements that apply, but if your customer doesn't have a specific scale, you're free to devise your own. At some point, someone decided on the scale you're using. What were the criteria involved? Why a 5-point scale (10 is the norm)? Since you have historical data, it should be used when you determine occurrence ratings. Since your customer is asking you to justify your numbers, you should be able to backtrack and determine the quantities and proportions of each type of failure. In the future, it would be a good idea to look at that data before you assign an occurrence number.

[jenna]

Jim, thank you for the quick response.

There are no specific requirements for medical device industry. The customer is our corporate office who has a very general requirement and allows us to devise our own scale, which in turn has to be justifiable. At some point in the past someone decided on scale that we are using (5-point is more usable for our world) and now we have to justify it or change it to something that is justifiable.

How do we go about using historical data to show that scale is applicable to our business?

[Jim Wynne]

In Reply to Parent Post by jenna

Jim, thank you for the quick response.

There are no specific requirements for medical device industry. The customer is our corporate office who has a very general requirement and allows us to devise our own scale, which in turn has to be justifiable. At some point in the past someone decided on scale that we are using (5-point is more usable for our world) and now we have to justify it or change it to something that is justifiable.

How do we go about using historical data to show that scale is applicable to our business?

I just realized (after rereading your original post) that you're being asked to justify the scale as opposed to any particular assignment of a value for occurrence. Is this correct? If so, you say that the 5-point scale is "more usable" for your situation. How did you make this determination? How can you say that it's more usable if you don't know why it's more usable? My suggestion, if you are indeed trying to justify the 5-point scale, is to use the more common 10 points, and justify it by way of the AIAG/SAE requirments as being a common standard, used in all sorts of businesses.