Tim Tyler wrote:
> Guy Hoelzer  wrote or quoted:
> 
>>in article ci7mqk$24qd$1{at}darwin.ediacara.org, Tim Tyler at tim{at}tt1lock.org
>>
>>>Guy Hoelzer  wrote or quoted:
>>>
>>>>in article chvng2$2hqs$1{at}darwin.ediacara.org, Tim Tyler at
tim{at}tt1lock.org:
>>>>
>>>>>Guy Hoelzer  wrote or quoted:
>>>>>
>>>>>>in article chsg65$1hqg$1{at}darwin.ediacara.org, Tim
Tyler at tim{at}tt1lock.org:
>>>>>>
>>>>>>>Guy Hoelzer  wrote or quoted:
>>>>>>
> 
>>>>>>Are you arguing that treating p_i as frequency is
almost never done,
>>>>>>or that this practice has not increased in
frequency?  Or are you
>>>>>>just arguing that you don't think it has become
sufficiently common
>>>>>>to call it a transition?
>>>>>
>>>>>p_i is /always/ the probability of the i'th symbol arising.
>>>>>
>>>>>Sometimes the probabilities are determined completly by symbol 
>>>>>frequencies - but the p_i's are never frequencies.
>>>>
>>>>If they are "determined completely by by symbol
frequencies" then they are
>>>>frequencies.
>>>
>>>A frequency is normally a measurement of the number of times that a
>>>repeated event occurs per unit time.
>>
>>I am aware of that definition, but I am using a different conventional
>>meaning.  This distinction might be a source of some of our differences.
>>The definition I am using is the one I believe to be most commonly used in
>>the biological sciences, and it well represented by the one
expressed by "A
>>Dictionary of Ecology, Evolution, and Systematics."  It reads:
>>
>>"The number of items belonging to a category or class; the number of
>>occasions that a given species occurs in a series of examples."
>>
>>This dictionary does not list any other definitions for
"frequency."
> 
> 
> I note that that still doesn't result in a series of numbers that add
> up to 1.0.
> 
Sorry, I didn't notice this earlier, but I've been caught out by this 
confusion in the past.  Basically, a frequency should be a count. 
However, one can talk about a relative frequency, which is a proportion 
of a total count belonging to one species.  In population genetics, 
frequency has been (mis-)used is this sense for a long time.

So, I think we just have to be aware that there is a mis-use of terminology.

Bob

-- 
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 68 (Gustaf H„llstr”min katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax:  +358-9-191 51400
WWW:  http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org
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