Dear MrQA,

Welcome to the forum !

I hv no idea what the "3 packers" standard(?) is but it appears to me that you are mixing 2, maybe, incompatible objectives -

(1) to conform to the legal requirements

(2) to "control" yr process by some rigorous, or at least semi-rigorous "statistical" procedure.

If you hope to involve any possibly interested readers in item (1), is the standard available anywhere on the web ? I seem to recall there are 2 basic methods typically involved, the t1/t2 procedure as referred in previous post and the (more empirical) procedure which usually was employed prior to any change to a t1/t2 system. I suspect you are discussing the earlier type system.

In the case of No2 the full approach is of course via SPC however this requires yr testing as to whether the process is in "control".

If you are merely trying to estimate what yr average fill volume is to some intrinsic accuracy, this is textbook statistics. As you probably know data is not discarded unless you can demonstrate the existence of outliers. The usual approach is to define a lot as per previous post and then use book formulae with yr own inputted accuracy requirements / trial guess. The calculation is slightly more involved if sampling is from "boxes" of bottles on a line but not horribly so (from memory). Offhand, the usual crude suggestion to achieve a "reasonably" accurate idea is to take around 30 samples, eg split (timed) uniformly across yr "lot" run, maybe 1 "random" bottle from each box and make the measurement / do the calculation. This is "systematic" sampling. Slightly biased from memory (?) but not bad. If you want more details on internal variations, need to take more bottles per sampling (2-stage / ANOVA etc).

Sorry if you knew all that already. Offhand, the adjustments you describe look "non-statistically" inspired, ie arbitrary.

Rgds / Charles.C

Definitely trying to conform to the legal requirements first and foremost , but also our own objectives as well. The standard is avail at:

http://www.legislati.../DLM301528.html but is very lengthy. Our SOP is this:

To ensure fill levels of all bottles produced meet the requirements of The Average Quantity System-Proposed Amendments to the Weights and Measures Regulations 1999. It is recognised that automated filling processes cannot fill every bottle to an exact amount over a production run, however the AQS aims to ensure that bottles do contain the amount stated on the label ‘on average’. Filling tolerances are proportional to the product size and difficulty of obtaining the correct fill, creating a standard which is fair to both manufacturers and consumers. **PROCEDURE:**The AQS has 3 basic requirements with which a production run must comply. If a sample taken from a production run fails any of these 3 requirements, the sample fails and the production lot fails (ie: does not meet the AQS requirements and must be reworked).1) The actual contents of the bottles in a production run must not be less, **on average**, than the quantity stated on the label.2) There must not be >2.5% **non standard** bottles in a run.3) There must be no **inadequate** packages.A non standard bottle contains less than the stated volume where the deficiency is greater than the set tolerance, but not greater than twice that set tolerance.An inadequate bottle contains less than the stated volume where the deficiency is greater than twice the set tolerance.The diagram below indicates tolerances for all bottle sizes filled. 187mL------------------------375mL-------------------------750mL-------------------------1000mL------------- Fill volumes falling within this band are acceptable providing the run passes the **average** test.178.6mL----------------------363.75mL---------------------735mL-------------------------985mL-------------- Fill volumes falling within this band are **non standard**, no more than 2.5% allowed.170.2mL----------------------352.5mL----------------------720mL--------------------------970mL-------------- Fill volumes falling below here are **inadequate**, none permitted.Ok...so our difficulty is at times , point 1) - and this is where the question of disregarding a result came up , if we retest immediately can it be done . My thought is no, but i've been asked to investigate. Agree with the latter half of your post , we are 'systematic sampling' and by and large it seems to work . However production people and QA people have different ideas about how to treat the data obtained, and the validity of such !