[Rasch] Models of unidimensional constructshavetheirlimitations:what is a "good thing"?

Stephanou, Andrew Stephanou at acer.edu.au
Fri Nov 9 09:32:14 EST 2007



Please do not take my statement out of context and generalise it. I was
observing that social scientists overwhelmed by the complexities of
their constructs tend to think that unidimensional measurement scales
are not suitable for them. They also tend to think that the constructs
used in the physical sciences are not complex ideas because they can
measure them easily.


I never said that the reading construct is simple. Thanks for the
details about it in your email.


For what concerns temperature, the definitions you mention are text book
definitions that refer to simple and specific contexts. I do not know
why you also mention heat. Heat is not temperature. The best I can do
for you is to refer you to a paper about the meaning of temperature and
how poorly it is understood by physics teachers.

Ralph Baierlein
&aqs=true> , The meaning of temperature, Physics Teacher, 28, 94 (1990)


I am aware of how little I know and understand both the reading
construct and the temperature construct.


I do not understand why you wrote that "neuropsychological test results
are affected by multiple factors, but usually age and education are the
only variables by which norms are stratified". Are you saying that to
construct a scale of reading ability I would need to know factors, such
as age and education, that affect the reading ability of people? The
construction of measurement scales, their qualitative description and
the measurement of the achievement of people on such scales is one
thing; the explanation of results of samples of people through
statistical modelling is another thing. To measure the height of people
I do not need to know their age, gender or socioeconomic status. After
the measurement, I need to make use of that information to make sense of
the results.  The scale of height is not sample dependent.




Andrew Stephanou

Australian Council for Educational Research

19 Prospect Hill Road, Camberwell VIC 3124

(Melbourne) Australia

phone: +61 3 9277 5568

fax: +61 3 9277 5500

email: Stephanou at acer.edu.au

web: http://www.acer.edu.au <http://www.acer.edu.au/> 



	From: rasch-bounces at acer.edu.au
[mailto:rasch-bounces at acer.edu.au] On Behalf Of Stephanou, Andrew
	Sent: Thursday, November 08, 2007 4:58 PM
	To: Agustin Tristan
	Cc: rasch at acer.edu.au
	Subject: RE: [Rasch] Models of unidimensional constructs
havetheirlimitations:what is a "good thing"?
	... Social scientists illude themselves if they think that
reading ability is a more complex construct than the construct of

Do social scientists delude themselves?
Is there a definition of the construct of "reading ability", which
stands independent of the method of its measurement, or are the rules
for measurement also partially constituent of the meaning of the
construct? I'm assuming the former .. but ... 
With regard to reading ability, is it possible to be able to read text
without comprehending what is being read? Is that "reading ability" or
something else? I note in the paper 
(2006) Reading ability mediates the relationship between education and
executive function tasks. Journal of the International
Neuropsychological Society , 12, 64-71.
Reading ability is measured by (p. 65) the 

"Wide Range Achievement Test-3 (WRAT-3): Reading (Wilkinson, 1993)

This is a test of word familiarity and sight reading ability involving
the pronunciation of a series of 15 letters of the alphabet and 42
increasingly difficult words. A maximum score of 57 is possible. As
reported in Spreen and Strauss (1998), it has been useful in estimating
premorbid intelligence, and moderately relates to WAIS-R IQ scores
(Griffin et al., 2002). " 
The abstract rom the paper reads ...
Neuropsychological test results are affected by multiple factors, but
usually age and education are the only variables by which norms are
stratified. Some authors have questioned whether these variables alone
are sufficient (e.g., Marcopulos et al., 1997; Manly et al., 2002),
since such norms have lead to problems, such as poor specificity for
African Americans on dementia screening devices (Fillenbaum et al.,
1990). Recent research has shown that reading ability, a measure of
educational quality, attenuated racial differences in test performance
(Manly et al., 2002). We specifically examined whether reading ability
would account for a greater amount of variance than education in
executive function tests in a population traditionally subject to poor
educational quality. Results determined that reading ability accounted
for a significantly greater amount of variance than years of education
for Letter-Number Sequencing, Similarities, COWA, Trail Making Test, and
Coloured Progressive Matrices. Reading ability was found to
significantly mediate the relationship between each of these tests and
Then there is the paper by 
van den Bos, K. P; Nakken, H; Nicolay, P. G; & van Houten, E. J.(2007)
Adults with mild intellectual disabilities: Can their reading
comprehension ability be improved? Journal of Intellectual Disability
Research. Vol 51(11) Nov 2007, 835-849 (which doesn't use Lexiles by the
Are we talking about an ability or a skill, or are these terms
Is reading ability actually a behavioral proxy for vocabulary knowledge?
What is comprehension, is it reading ability or another variable which
requires separate measurement?
Look at the corresponding definition of temperature; Giancoli (1988)
defines it as:
"how hot or cold an object is" .. (p. 406) and on page 449 "Temperature
is a measure of the average kinetic energy of individual molecules"
where on page 449, heat is defined as referring to: "the amount of
energy transferred from a hot body to a cold body" 
Howerver, defining "energy" is not so simple!
Perhaps reading ability is as complex as defining "temperature" - when
"average kinetic energy of molecules" is unpacked for meaning?  Maybe
even more so when that heady mix of "variables" like comprehension,
sight/phonic reading (without comprehension), vocabulary, and reasoning
are all taken to be constitutive somehow of the observed "reading
Or, do you claim that the Lexile system alone now defines (by its
application) the construct "reading ability"? I would guess Andrew
Kyngdon might want to make some statements here also.!
Regards .. Paul
Giancoli, D.C. (1988) Physics for Scientists and Engineers with Modern
Physics. 2nd Edition. Prentice-Hall. 


Paul Barrett, Ph.D.

2622 East 21st Street | Tulsa, OK  74114

Chief Research Scientist

Office | 918.749.0632  Fax | 918.749.0635

pbarrett at hoganassessments.com


hoganassessments.com <http://www.hoganassessments.com/> 





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