If you have not read this article by Lo-Decarie et al. in the latest
issue of frontiers in ecology and environment, it a pretty good
papper.
They note that r2 values have fallen over the years as it has become
statistically more complex. .
This feeds back to two problems I have noticed in perusing the
literature over recent years. First, although we like to proclaim a
lot of data-heavy research, the truth is that many ecological studies
really do not involve large numbers, samples and for that matter
replicates. This can be out of necessity, so I am not criticizing it
entirely, however, there are times when it would be better, as Bob
Jaeger once told me, to increase the replicates and simplify the
question. In any case, that is also not always possible.
Another issue with this I personally have is the use of probability
theory and point-based estimates where it really is not appropriate.
This has been a growing issue in ecology. There are times to use
probabability, but there are also times when it should be left aside
for other methods such as possiblity theory due to the large degree of
uncertainty. OFtentimes it would be better to fuzzify the data or use
interval analysis in place of the point-based methodology.
However, despite decades of discussion in this thread, widespread
adoption of the approach in engineering, computer science, and
virtually every other area of inquiry, ecology remains decidedly
behind the curve, still binding itself to virtually exclusive use of
probability theory and point-based estimates. The movement to CIs is
even pretty slow, and most are still stuck in the archaic decision
theory mold. This latter area is fine for simplistic studies and
early understanding of statistics. However, if you ignoring the
uncertaintly that undoubtedly prevails in the system, you have no clue
if your inputs are legit or if your outputs are realistic.
So, when you see r2 values falling over time, it is probably a good
thing to consider we may be overly dependent on point-based estimates
and probability theory.
--
Malcolm L. McCallum, PHD, REP
Department of Environmental Studies
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