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st: RE: Ecological monitoring


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Ecological monitoring
Date   Mon, 5 Aug 2002 12:01:08 +0100

Graham M Smith
> 
> This is probably a very broad question so I will be 
> grateful to anyone who has the time to answer. I also 
> apologise for its length
> 
> A lot of ecological monitoring is undertaken by consultants 
> with limited statistical abilities, even though it often 
> involves a fairly sophisticated design. eg 10 transects 
> with 5 sampling stations per transect, 10 samples collected 
> from each Station, and samples collected 4 times a year for 
> 5 years. Some of the transects might be impacted upon by 
> development and you are trying to compare those with the 
> ones not impacted upon. Or all transects might be impacted 
> upon and it is a before and after type study. 
> 
> An unsophisticated  approach to this, that I have often 
> seen done, is to aggregate the results in a manner that 
> allows an ANOVA to be done, usually Kruskal Wallis, or if a 
> statistician is involved - to use a mixed effects model 
> usually in SPlus.
> 
> I have just started to read Lohr "Sampling: Design and 
> Analysis" and discovered the facility in Stata to analyse 
> survey sample data, which would seem to be an extremely 
> useful tool for analysing environmental or ecological data. 
> Yet I know of no one in the environmental/ecological field 
> that uses Stata, or indeed programs like Sudaan. A quick 
> poll of the professional statisticians I know (n=5)that 
> work in ecology came up with a "never heard of Sudaan" 
> "don't know anything about Stata" "can't see it doing 
> anything that proper programming in S-Plus can't do"
> 
> However, I am personally still interested in exploring this 
> further. I am not a statistician, but I am interested in 
> the design and analysis of cost effective and robust 
> ecological/environmental monitoring programs. I have a 
> reasonable understanding of statistics but it falls short 
> of writing S-Plus programs and mixed effects modelling.
> 
> Is anyone here using Stata in an ecological or 
> environmental field (eg Pollution studies) and do the tools 
> in Stata for analysing Survey sampling data offer something 
> valuable to the analysis of ecological data. Not everyone 
> has the skills or time to write an SPlus program - even if 
> it can be done.
> 
> Any way, I would be grateful if anyone  can provide some 
> comments on this, and improve my understanding of Stata and 
> the use of its Survey Sampling routines.
 
There are Stata users with primary interests in environmental 
applications. I am one. At the same time, such users appear 
to make up a fairly small proportion of the Stata community. 
I don't recollect anybody with a specific interest in 
ecological monitoring. In contrast, S-Plus does have a 
substantial presence in (its own definition of) 
environmental statistics. 

More specifically, I can't advise in detail on the usefulness of 
Stata's -svy- commands for looking at ecological monitoring. 
I would want to worry about their applicability to 
situations with strong spatial and temporal element. However, 
from what you say, these elements are often ignored in practice. 

Stata is programmable; S-Plus is programmable. 
Those who have programmed in both -- and that doesn't 
include me -- might comment on the differences. 
But if the issue is using Stata's -svy- commands 
versus replicating them by programming in S-Plus, 
then my guess is that the latter would be a very 
great deal of work.  

Nick 
n.j.cox@durham.ac.uk 
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