[Taxacom] sloppy cladistic analyses

[Stephen Thorpe]

>Stephen: "systematics which depends heavily on "number crunching". They have a tendency to lose the "narrative" - a huge data matrix and associated tree are not a narrative!" I am guessing that you mean a prior hypothesis of relationships somehow guiding (= massaging) the data til the "congruent" answer emerges? The "fleshing-out" of each step speaks of a posteriori interpretation so I am unsure.

No, I didn't mean that! I mean that giving a huge numerical dataset and saying "this is what comes out of the analysis" leaves us with little hope of spotting errors, and a high probability of coding errors happening, as lots of numbers don't mix well with scientists in a hurry. A "narrative" doesn't mean a preconceived wish for a desired conclusion, it means using words to explain each step of the process so that we can understand and follow the steps that lead to the conclusion...

Back to my dungeon!

Stephen

________________________________________
From: taxacom-bounces at mailman.nhm.ku.edu [taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Jason Mate [jfmate at hotmail.com]
Sent: Thursday, 4 February 2010 11:57 a.m.
To: Taxacom
Subject: Re: [Taxacom] sloppy cladistic analyses

I mistakenly sent my previous email to Ken, but I have changed it in light of recent postings.

Ken:
-Define "information" versus information.
-Linked characters matter a lot more than coding mistakes (as long as these mistakes are random and not somehow biased due to the reasearchers preconceived ideas)
-I have never taken information from the internet seriously.

John: "...but in the absence of any demonstrated evidence to the contrary I won't lose sleep worrying about that with respect to the current phylogeny produced by a particular analysis." I believe they call it congruence (or lack of in some cases).

"...'law of large numbers' that overrules the 'law of shared derived characters'..." They are not laws, they are more like guidelines... Seriously, the old quality versus quantity?


Stephen: "systematics which depends heavily on "number crunching". They have a tendency to lose the "narrative" - a huge data matrix and associated tree are not a narrative!" I am guessing that you mean a prior hypothesis of relationships somehow guiding (= massaging) the data til the "congruent" answer emerges? The "fleshing-out" of each step speaks of a posteriori interpretation so I am unsure.

Back to my hole.

Jason

> From: kennethkinman at webtv.net
> Date: Tue, 2 Feb 2010 21:18:44 -0600
> To: taxacom at mailman.nhm.ku.edu
> Subject: [Taxacom] sloppy cladistic analyses
>
> Dear All:
>       Although I don't ALWAYS agree with Michael Mortimer, his cladistic
> analyses are far better than most.  Therefore, I find his following
> critique of many recent cladistic practices and shortcomings very
> seriously.  It reflects a broader problem among computer generated
> so-called "information" and an alarming trend of  internet
> DISINFORMATION now competing with or even outpacing good information.
>        What one now finds on the internet, including scientific
> information, must increasingly be taken with a huge grain of salt.  The
> truism about computers in the hands of more sloppy users is
> unfortunately an increasing reality:  "garbage in, garbage out."  This
> is certainly true of cladistic analyses by those who just don't
> critically evaluate the codings of previously analyses and just cut and
> paste them and add a few of their own.  Adding a little new information
> to a database riddled with garbage, and the garbage can overwhelm the
> new information (whether the new information might be helpful or not).
> As Mortimer says, it can give a false impression of consensus in
> something that may or may not be true.  Here's a link to his concerns:
>
> http://dml.cmnh.org/2010Feb/msg00010.html
>
>
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