Should volume of sales be factored into risk probability assessments?

Mark Meer

Trusted Information Resource
#1
Wondering aloud: would it make sense to factor in an estimated volume of sales and/or number of users and/or number of procedures when considering harm probabilities?

We've never done this (and I'm curious if anyone does), but does seems reasonable in some way.
That is, the probability occurrence of a harmful event is proportional to the device's use.
All else being equal, a device that is used by millions presumably has a much higher probability of issues that a device that only has a few hundred users.

Curious what others think...
 
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atitheya

Quite Involved in Discussions
#2
Wondering aloud: would it make sense to factor in an estimated volume of sales and/or number of users and/or number of procedures when considering harm probabilities?
To my understanding,

Where-ever there is a possibility of harm, there is risk. If business augmentation creates a possibility of harm, it must be identified and steps taken to mitigate / minimize that risk. Such as in

All else being equal, a device that is used by millions presumably has a much higher probability of issues that a device that only has a few hundred users.
If such a situation may lead to a hazardous situation of users not being serviced / troubleshooted in time resulting in some harm (as may be determined by you) then may be one can increase the service team size or take any other action to mitigate or minimize the risk.

Of course, (on a lighter note), you will not refuse to increase your volume because of such a risk. :D

Just my opinion. Let’s hear from others too.
 

Mark Meer

Trusted Information Resource
#3
...If such a situation may lead to a hazardous situation of users not being serviced / troubleshooted in time resulting in some harm (as may be determined by you) then may be one can increase the service team size or take any other action to mitigate or minimize the risk.
This isn't quite what I was thinking, but it is certainly another consideration I hadn't thought of. ;)

What I was thinking may be illustrated through a hypothetical example:

Say that a power-supply's fault rate is estimated at 1 in 100,000. If I have a device that sells millions of such units, then the probability of harm resulting from such an event may make the risk unacceptable, whereas if I only sell a couple hundred units the risk may be evaluated as acceptable.
 

Tidge

Quite Involved in Discussions
#4
Wondering aloud: would it make sense to factor in an estimated volume of sales and/or number of users and/or number of procedures when considering harm probabilities?
The volume of sales should not factor into either P1 or P2. A large volume of devices can help inform P1 and P2 (because of a larger denominator) but that would be the extent of value in determining risk (not harm).

You can try to factor volume into a risk-benefit analysis, but this can be a double-edged sword. On the surface: a device which is universally used with only a small fraction of patients/users experiencing harm may seem like a good thing ("look how safe it is!") but as devices become more common there is an onus to reduce the risk for even higher fractions of patients/users... it can become less acceptable to tolerate risks that may have been acceptable when the device was more 'bleeding edge'.
 

Mark Meer

Trusted Information Resource
#5
... it can become less acceptable to tolerate risks that may have been acceptable when the device was more 'bleeding edge'.
This is sort of what I was getting at: volume of sales (or estimated number of users/procedures) seems like a salient variable when determining acceptability criteria as a 1 in 100,000 probability may be acceptable for sales in the hundreds, but unacceptable for sales in the millions.

I still think there is an argument that this could be factored into probability of harm, as the more users there are the greater the probability of any event leading to a hazardous situation manifests.
 

yodon

Staff member
Super Moderator
#6
Say that a power-supply's fault rate is estimated at 1 in 100,000. If I have a device that sells millions of such units, then the probability of harm resulting from such an event may make the risk unacceptable, whereas if I only sell a couple hundred units the risk may be evaluated as acceptable.
That would imply that you have control over when the faulty ones are distributed. You've (presumably) already determined that the risk of 1 in 100,000 is acceptable. You wouldn't sell 99,000 then say "we can't sell any more because we know the next one will fail."
 

Jim Wynne

Staff member
Admin
#7
Further to the point @yodon made, when the probability of some phenomenon is 1 in x opportunities, and failure is random, the one failure might happen in the first instance, the 100,000th, or anywhere in between (or not at all).
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#8
Yodon and Jim are touching on the real issue here. Math.

Increasing sales - or usage of a product - doesn't change the probability of a failure or the the occurrence rate. It changes the NUMBER of failures.
IF harm is not a certainty of a failure but is a proportion of occurrences then the same math applies. increasing sales/usage will increase the NUMBER of events that result in harm. not the probability.

This can of course increase the cost of dealing with the failures as that is tied to the number and not the proportion of sales/uses. It can I suppose increase the 'probability' that the Customer base or the media or facebook hears about the failures and gets mad at you.

Your organization may find that 1 harmful is acceptable and 10 isn't based on cost reputation or whatever. .. so increasing sales will factor into your decision. but that has nothing to do with probability. Our words matter, let's use them correctly.

Math matters and it counts.
 

Mark Meer

Trusted Information Resource
#9
Increasing sales - or usage of a product - doesn't change the probability of a failure or the the occurrence rate. It changes the NUMBER of failures.
IF harm is not a certainty of a failure but is a proportion of occurrences then the same math applies. increasing sales/usage will increase the NUMBER of events that result in harm. not the probability.

This can of course increase the cost of dealing with the failures as that is tied to the number and not the proportion of sales/uses. It can I suppose increase the 'probability' that the Customer base or the media or facebook hears about the failures and gets mad at you.
I think the numbers matter, over and above simply media, facebook, or company reputation/cost considerations. We are, afterall, dealing with real-world harm to individuals...

I take your point @yodon that you have no control over distribution, but assuming a random distribution, if a failure mode that could result in death has a probability of 1/100000, then if only 10 units are sold, the probability of this manifesting is remote, whereas if millions of units are sold then it's an almost certainty that someone is likely to die. In this sense we are talking about the probability that someone dies, no?

Could it not be the case that the former case is deemed acceptable, but the latter is not?
 

yodon

Staff member
Super Moderator
#10
I'll still say no because it's already been determined that this IS acceptable. We are dealing with medical devices and the fact is that there is a chance for death. If it's not acceptable, you need to take additional measures to reduce the risk.

For the sake of argument, let's say you somehow DO increase the likelihood of occurrence at some point based on a sales threshold being reached. What would you do? Stop selling? Implement new controls? THAT would really bother me if I was one of the ones to get the device before the threshold was met. And it would no doubt open you up to litigation.
 
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