[Rasch] Units of measurement in the social sciences

Trevor Bond trevor.bond at jcu.edu.au
Wed Oct 17 08:57:27 EST 2007


At 11:26 AM -0700 10/16/07, Anthony James wrote:
>Dear folks,
>Another dumb question...
>I'll be grateful for any comments.
>When we are talking about "units of measurement" in the physical 
>sciences we are talking about some tangible things. (I avoide the 
>word "concrete" because I know you don't like it in this context and 
>argue that all measures are abstractions). However, I mean kilo or 
>meter , for example, are understandable attributes that have a 
>concerete existence. A "sample meter" ,i.e., a rod of 1 meter can be 
>aligned with any object and count the number of alignments. Or we 
>can put some potatos on the pan of a scale and put enough weaights 
>on the other pan until the beam is balanced.

Sure, there are fundamental measures in the physical science (e.g. 
weight, length, volume) which can be physically concatenated as 
described by Anthony; but there are other derived physical science 
measures (e.g. density, temperature) for which physical concatenation 
does not work:

1l water @ 50oC weighs 1kilo and has a density of 1.0

add another identical one to get:
2l water weighing 2kilo with a density of 1.0 and the temp at 50oC

Still - a good (not dumb) question, Anthony!
best wishes
TGB


-- 
Trevor G BOND Ph D
Professor and Head of Dept
Educational Psychology, Counselling & Learning Needs
D2-2F-01A EPCL Dept.
Hong Kong Institute of Education
10 Lo Ping Rd, Tai Po
New Territories HONG KONG

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