Units for Counts & proportions

Mon Nov 18 09:23:48 PST 2002

David,

there is a history behind "amount".  It was, I believe, created
specifically to mirror one of the NIST fundamental types:  amount of
substance.  "moles" is more than just an example:  it is intimately tied
up with the effort to quantify extent of material.  I think it would be
a misuse of "amount" to invoke it as a representation of "count".  We
have another unit, as someone has pointed out, called "number", which is
probably more appropriate.  I'm not going to make any recommendation
about how to represent a proportion, but I think not even
numberPerNumber is a complete solution.  Number sounds inherently
discrete, whereas many proportions are continuous.  Incidentally, the
distinction between discrete and continuous is another issue that is
ambiguous in the Stevens typology.  Ordinal gets treated both ways,
depending on context. (Personally, I think categorical vs. continuous is
a fundamental distinction  that gets ignored.)  Thanks for your previous
article and link:  it brought out several other issues with the Stevens
typology that needed mention.

Tim.

> David Blankman wrote:
> 
> I have been looking at eml-unitDictionary.xml. I noticed that there is
> a fundamental unit type called  "amount".  Since the documentation on
> "amount" references "mole" as an example, and since a mole is a count
> (6.x * 10 ^23) of things, then it seems to me that the appropriate
> dimension for count  must be "amount" (unless I have misinterpreted
> what the unit type "amount" signifies).
> 
> If that is the case, then a proportion can be derived from amount, as
> maybe, amountPerAmount  or something like that.
> 
> Does that make sense?
> 
> David
> 
> Peter McCartney wrote:
> 
> > Agreed - in this case "cells" could be identified as the domain,
> > perhaps. It would be nice if we could find a way to make the
> > dictionary more extensible without having to start from scratch each
> > time we want to make a ratio or a density against an already defined
> > unit.....
> >
> > We have a similar problem with proportions which are similar to
> > densities except they are against an arbitrary number that
> > represents a "whole". I think we left off last week deciding to also
> > treat counts and proportions as ratio scale and use some sort of
> > unit (dimensionless?). Is that right? it seems like we need some
> > more unambiguous identification of counts and proportions comparable
> > to what we have for densities (we have a unit type defintion for
> > density,but not for counts or proportions.
> >
> > Peter McCartney (peter.mccartney at asu.edu)
> > Center for Environmental Studies
> > Arizona State University
> > 480-965-6791
> >
> > > -----Original Message-----
> > > From: Chad Berkley [mailto:berkley at nceas.ucsb.edu]
> > > Sent: Wednesday, November 13, 2002 9:01 AM
> > > To: Dan Higgins
> > > Cc: David Blankman; Chad Berkley; Tim Bergsma; Eml-Dev (E-mail)
> > > Subject: Re: Found something that should go in unit
> > > dictionary (I think)
> > >
> > >
> > > Hi David and Dan,
> > >
> > > Dan, you're right.  There is already a unitType called
> > > volumetricDensity which
> > > is essentially a numberPerVolume.  Unfortuneately, there is no
> > unit
> > > numberPerMilliliter, only numberPerMeterCubed.  So David, we
> > > can add the unit
> > > numberPerMilliliter but like Dan said, it would be impractical to
> > add
> > > XPerMilliter where X could be anything.  We should probably
> > > add number per
> > > Milli, micro, ...,kiloliter while we're at it.
> > >
> > > chad
> > >
> > > Chad Berkley
> > > Metadata Systems Developer
> > > National Center for Ecological Analysis and Synthesis
> > > 735 State St. Suite 300
> > > Santa Barbara, CA 93117
> > >
> > >
> > > Quoting Dan Higgins <higgins at nceas.ucsb.edu>:
> > >
> > > > Hi David,
> > > >     Isn't the unit here really 'number per milliliter' rather
> > that
> > > > 'cells per milliliter'. (i.e. just a number density) Cells
> > > is the thing
> > > > being counted. Otherwise, one would have units of 'tadpoles
> > > per liter',
> > > > 'apples per square mile', 'oranges per acre'. etc with a
> > > different unit
> > > > for every possible thing that one might want to count.
> > > >
> > > > Dan Higgins
> > > >
> > > > ---
> > > >
> > > > David Blankman wrote:
> > > >
> > > > > Chad and Tim,
> > > > >
> > > > > I am starting to do EML conversions for the McMurdo LTER.
> > > They have a
> > > > > number of data tables  that relate to plankton. The unit
> > > that they use
> > > > > is cells/milliliter. I am guessing that this is a unit
> > > that others
> > > > > might use.
> > > > >
> > > > > David
> > > > >
> > > >
> > > >
> > > >
> > >
> > >
> > > -------------------------------------------------
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> > >
> >
> 
> --
> David E. Blankman
> Database Integration Developer
> Long Term Ecological Research Network Office
> University of New Mexico
> 801 University, SE #104
> Albuquerque, NM 87106
> (505) 272-7346 / (505) 272-7080 FAX

-- 
Tim Bergsma
LTER Information Manager
W.K. Kellogg Biological Station
Michigan State University
Hickory Corners, MI   49060
616/671-2337
tbergsma at kbs.msu.edu
http://lter.kbs.msu.edu