1/30/2024 0 Comments Probability of risk occurrence![]() Multiple things need to happen at the same time.ĭan has done a great job with his explanation, but much more can be said. The sequence of events means it is not a single point event. In medical device risk management the hazard could be in either a normal or a fault condition. It only considers single point failures (fault condition). However, an FMEA is not the right tool for medical device risk management. Typically, an FMEA uses P only and usually defines it in an interval. So, in practice, estimate the interval for P or do a lot of contortions that end up with an estimate of the interval for P. The underlying distribution in uniform across the interval. The convention is that P is not a point estimate, but a range of values typically covering an interval that is an order of magnitude. How do you estimate the probability of touching the exposed wire – P 2? Next, a person plugs something into the outlet without the cover plate, touches an exposed wire, and gets a shock (the harm). How do you estimate the probability of failure to put the cover plate back – P 1? Unfortunately, she forgot to put the cover plate back. An electrician comes in, troubleshoots the problem and leaves. There is a problem with a wall outlet in the meeting room. The problem, in the point estimate case, is that you multiply a very small number by another very small number to get a very very small number. Consider how you would multiply two normal distributions with different means and different standard deviations to get the resultant distribution. That integral can be very hard to compute. However since they are really distributions, their product is the convolution of the distributions. If you have point estimate then multiply them together. In addition, a point estimate is the wrong model it should be a distribution. Again, it should be a small probability – one occurrence in 10,000 times. This results when the patient or user is exposed to the hazardous situation. P 2 is the probability that the hazardous situation leads to a harm. However, it should really be a statistical distribution. In addition, it is usually characterized as a point estimate. In practice, it is a hard number to estimate. This means that all items in the sequence must occur at the same time. The steps in the sequence of events should, collectively, be a small probability – say one occurrence in 10,000 times. P 1 is the probability of a hazardous situation associated with the hazard mediated by the sequence of events. The process is to identify a hazard, a sequence of events leading to a hazardous situation, a hazardous situation leading to a harm. In practice there are a few difficulties. Figure C1 shows a conceptual diagram, not a practical application. ![]() The concept is pedagogical and not practical.įirst, ISO 1497:2019 Annex C is informative. There are no circumstances in which you should use P 1 and P 2. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |