At risk of being (pretty rightly) accused of
getting involved in something about which, in detail, I know very little (I'm a
very amateur bird-watcher, though I do have qualifications in science and
economics of some relevance to the question I'm asking!), I would be interested
to know something about the statistical "reliability" of the data shown in the
last few days on rufus and golden whistler population time series trends and
population seasonalities. My sense is that only if the data are
statistically sound can reasonably reliable general conclusions be inferred from
them. (I'm not for one moment suggesting there is
a "reliability problem" - it's just that I've not seen any comment on the
question, either way).
I am wondering (a) what sample sizes are
these data based on - essentially how many actual bird sitings and how many
"nil" sitings from how many observation sites/areas are represented by each data
point on the graphs; and (b) what proportion of the "area/region of
interest" (eg, the ACT if it's trends in the ACT that are being
reported) - or perhaps more usefully what proportion of the species'
typical habitat' in (say) the ACT, was included in the aggregate
I ask these questions, in part due to prior
experience in ostensibly scientific data and analyses on Southern Bluefin Tuna
(SBT) population, when I was involved as a policy adviser in trying to interpret
the analyses from what had turned into a major dispute between Australian
and Japanese fish population scientists over SBT populations and
"responsible" fishing quotas.
To simplify the detail of the analysis, the dispute
turned on significant differences in the two countries' scientists'
methodologies in estimating (and projecting) current and future SBT
populations. In part, an element in the different analyses and conclusions
was the extent to which population data from a set of "sample areas" which
necessarily covered only a small proportion of the total range of SBT could, or
could not, be regarded as "representative".
So, to put my questions that way, can you be
confident that the whistler (both species) sample areas used in the
data/analysis that have are now being presented and discussed are
"representative" enough , and the number of sitings made (whether positive or
not) large enough to enable reliable inferences to be drawn?
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