For Class A and B areas, the assorted compendia will give you the
Pass/Fail limits. FDA, for one, is "recommending" (ha-ha) that you set
your own Alert limits (or, if you use 3 levels, Alert and Action limits)
below those, based on your own results and history. We have set Alert and
Action limits based on 95% and 99% levels (2sd, 3sd). The limits in "B"
areas are differentiated between "surface" and "floor" sites, but not
beyond that; all "A" areas have the same limits. For "C" or higher areas,
the limits are all set statistically.
This means, for every place I have seen, that the Alert and Action limits
in force are MUCH lower than-- frequently only a FRACTION of--the
compendial limits. This, in turn, produces loud squawks of protest from
Operations personnel- but figures don't lie, if people and facilities
have produced consistently-low results over the course of years, there's
no reason to expect high levels of Alerts if you set the limits
accordingly. And, in fact, history shows the expected numbers- if you set
99% Action limits, about 1% of the results will be Action level.
[log in to unmask]
On Fri, 19 Dec 2003 13:46:16 -0500 "Boschi, Francesco"
<[log in to unmask]> writes:
> Dear list,
> I would like to receive some advices about setting alert and action
> for environmental monitoring program in an injectable department.
> Which statistical approach do you apply (normal distribution,
> exponential distribution, ...) ? Do you set different levels for
> location (very difficult to manage, I guess) or you consider all the
> from the same grade locations ? Are you required to set
> statistically levels
> for all classes (for grade A and probably B it does not sound very
> meaningful ...) ?
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