> I'd like to add the clarification that the accuracy of NMD (and any
> other mite assessment method) is largely dependent upon taking
> a series of samples in order to track trends, rather than counting
> on any single sample as a "snapshot."
That is critical to understanding what we measure. Many of us who
understand -- or think we understand -- mite dynamics speak blithely
about one reading, but we are always extrapolating what is happening
over time before and after that reading, and its probable accuracy,
based on experience.
Often we do not state our assumptions and that can lead to errors in
understanding by those listening.
The interpretation of any measurement of an ongoing process necessarily
depends on assumptions. By nature, people tend to assume a steady
state or linear process when that may be far from what is really happening.
Changes in brood area, queenlessness, swarming, manipulations, moving,
poisoning, robbing by or of other hives, treatments, skewed bee or mite
population demographics and many other factors may render our assumptions
invalid.
It takes three observations to establish a series, but may take more than
that if the series is random or non-linear, and without doubt, mite population
growth has both these characteristics at times.
We use crude, easy methods to obtain the information we need to make
judgments, and usually they are sufficiently accurate for our purposes,
particularly when observations are averaged over time and a number of
colonies.
Nonetheless, any attentive observer who has used either of these methods
has seen anomalies sufficiently surprising to realise that an one reading
or small set of readinsg taken alone can be very, very deceptive.
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