[Rasch] Bunched versus spread out items to measure depression

Rense Lange rense.lange at gmail.com
Sun Jul 24 14:44:30 EST 2011


There seem to be two things here: a) whether response patters truly define quantitative differences, and b) DIF between patient and non-patient groups warrants rejection of single dimension. How would we go about finding out about this?

On Jul 23, 2011, at 11:19 PM, Paul Barrett wrote:

> I’m curious about how many seem to be  understanding ‘Depression’, with relevance to an individual who is very (clinically) depressed (showing physiological/chronometric/attentional deficits, hippocampal neurogenesis attenuation, as well as affective disturbances) and someone who just feels a bit ‘down’.
>  
> To assume that the ‘state of ’ depression varies additively, with equal-interval ‘units of depression’ forming linear magnitudes of affect, is a huge assumption, which needs empirical and experimental justification. The fit or otherwise of the Rasch model to a set of self-report item responses is not the same as stating that something which might be called “Depression” varies additively. That latter statement  requires a different kind of empirical evidence altogether.
>  
> Anyway, for a very nice discussion concerning the Beck,  and the concept of Depression as a ‘variable’, try Hammond, S.M. (1995) An IRT investigation of the validity of non-patient analogue research using the Beck Depression Inventory. European Journal of Psychological Assessment, 11, 1, 14-20.
> Abstract
> This paper presents an IRT analysis of the Beck Depression Inventory which was carried out to assess the assumption of an underlying latent trait common to non-clinical and patient samples. A one parameter rating scale model was fitted to data drawn from a patient and non-patient sample. Findings suggest that while the BDI fits the model reasonably well for the two samples separately there is sufficient differential item functioning to raise serious doubts of the viability of using it analogously with patient and non-patient groups. 
>  
> Regards .. Paul
>  
> Advanced Projects R&D Ltd.
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> From: rasch-bounces at acer.edu.au [mailto:rasch-bounces at acer.edu.au] On Behalf Of Rense Lange
> Sent: Sunday, 24 July 2011 1:44 p.m.
> To: Ian Wilson
> Cc: Rasch
> Subject: Re: [Rasch] Bunched versus spread out items to measure depression
>  
> This is not to defend the Beck, but I must disagree in general. The Rasch measure defined by the Beck raw scores (provided the items fit the model, etc) IS a quantitative variable. I grant you, there are only n+1 (where n = # questions) point that are defined. When the same no of questions are used, questionnaires using rating scales differ wrt the number of defined points on the Rasch dimension, true enough. But, there is no inherent qualitative difference, just one of resolution / granularity. Add more dichotomous questions to the Beck, and you can have the same resolution (at least locally) as any rating scale based measure. Caveat: It is difficult to say beforehand how many dichotomous questions should be added to achieve equivalence, as this depends on what is meant by resolution, equivalence, item properties, # categories, etc.
>  
> Rense Lange
>  
>  
> On Jul 23, 2011, at 8:15 PM, Ian Wilson wrote:
> 
> 
> Hi Agustin
> The problem is that the Beck produces a dichotomous result – Depression Yes or No.  It does not produce levels of depression.  For that you need another instrument such as the K10 or DASS
> Regards
> Ian
>  
> Ian Wilson
> Professor of Medical Education
> School of Medicine
> University of Western Sydney
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>  
> From: rasch-bounces at acer.edu.au [mailto:rasch-bounces at acer.edu.au] On Behalf Of Agustin Tristan
> Sent: Sunday, 24 July 2011 11:05 AM
> To: Michael Lamport Commons; Rasch
> Subject: Re: [Rasch] Bunched versus spread out items to measure depression
>  
> Hello!
> Sometimes I would like to have a better way to explain myself in English and try to transmit my ideas regarding the problem you're facing actually, I hope this time I shall be clear enough.
> The idea of the design of a test is important for everyone and validity is the main and first property for many of us. Nevertheless I think we are not following a former idea by Ben Wright that is presented in several documents concerning the item distribution and all the implications this simple concept has regarding the other characteristics of measurement.
>  
> An investigator produces a test with N items for a specific construct (depression in this case), using partial credit, dichotomous or any other kind of items. He uses the questionnaire with M persons and passes the responses through the Rasch model using a good software (independently of the brand: Winsteps, Rumm, Rascal, your own software...) and he gets measures that are intended to be in a linear scale. The distribution of the measures of the persons or the individual measures will be interpreted according to the scale and the item measure will give some interpretation concerning depression in this case. This is ok...wait! is this ok? what is the problem with this? It is related to validity.
>  
> We have used the Beck depression questionnaire (and also the suicide scale and other scales), that are supposed to correctly measure depression (or suicide), but what we have found is that the Beck scale is satisfactory only for "depressed" people. But if we use it with what we could call "normal or non depressed " persons, then test is useless.
> Do I have to wait that my young students become depressed if we want to detect them with the Beck questionnaire?
> Do I have to wait that my car tank is empty to decide that I have to go to the pump station?
>  
> The persons distribution, and the SE may say something but only if I am in a certain portion of the scale, because the questionnaire does not have items covering all the possible states from "normal" to pathologically depression. Ben Wright suggest to have items covering all the scale and not only a portion, unless I want to use the scale on depressed persons.
> Item distribution is related to the test design line, an idea proposed by Ben but not used everywhere and not conceptualized as a theoretical concept.
> I can notice that we accept the Rasch model as a theoretical expected model of an item and, curiously,  we do not accept that there should be also a theoretical expected model for a test (the test design line is that model). That is whay we can accept tests with a bad distribution of items, with a defficient scale, because we are convinced that the Rasch measures permit to define ALL the scale, even if the set of items is not sufficient to describe the construct.
>  
> Without the theoretical test model, we try to explain the problems with the Beck's measures (or the suicide, etc.) as a function of the SE, or probably as a consequence of the sample, or perhaps because we may think that it is not Guttmann, or probably because the Cronbach's alpha was 0.3, or probably because they copied the answers, or probably because we have to wait that our students become sufficiently depressed if we wish to measure them using Beck or Hamilton questionnaires... and all those explanations may be false, because the basics of the scale is wrong.
>  
> I cannot understand how we can try to explain the planetary system unless we understand that the planets translate around the Sun. Everything about the planets comes from this concept, otherwise we can give explanations that are very complicated and someday will fail.
> I cannot understand how we can try to explain the results of a test unless we use the test design line as a necessary coondition for the scale's validity. Everything about test and persons measures comes from this concept, otherwise we can give explanations that are very complicated and someday will fail.
>  
> I've presented the tests design line and all its implications elsewhere...It works.
>  
> Regards
> Agustin
>  
>  
>  
>  
>  
> 
> 
>  
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> --- On Sat, 7/23/11, Michael Lamport Commons <commons at tiac.net> wrote:
> 
> From: Michael Lamport Commons <commons at tiac.net>
> Subject: Re: [Rasch] Bunched versus spread out items to measure depression
> To: "Bond,Trevor" <trevor.bond at jcu.edu.au>, "Bond,Trevor" <trevor.bond at jcu.edu.au>, "rasch" <rasch at acer.edu.au>
> Cc: "Jose Alves" <alves at psi.uminho.pt>, "Jose Alves" <alves at iep.uminho.pt>
> Date: Saturday, July 23, 2011, 6:25 AM
> 
> We had people with a very wide range of depression from none to a lot.  We had a sample from listservs for depressed people and regular depressed people.  It might be that depression is not Guttman like, i.e. one does not have to be a little sad before one cries a lot and skulks, and before one stops leaving ones room.  We found it was just about how many items with about the same Rasch score predicted the amount of depression.  Many of the common depression scales such as the Hamilton and Beck seem to have the same property when we Rasch analyzed them.''
> 
> MLC
> 
> -----Original Message-----
> >From: "Bond, Trevor" <trevor.bond at jcu.edu.au>
> >Sent: Jul 23, 2011 3:15 AM
> >To: "Bond, Trevor" <trevor.bond at jcu.edu.au>, Michael Lamport Commons <commons at tiac.net>, rasch <rasch at acer.edu.au>
> >Cc: Jose Alves <alves at psi.uminho.pt>, Jose Alves <alves at iep.uminho.pt>
> >Subject: Re: [Rasch] Bunched versus spread out items to measure depression
> >
> >Ooops drinking champagne at breakfast time:
> >Large person SE (sic.)= too few items. Or huge targetting problem
> >
> >
> >On 23/07/11 8:39 AM, "Bond, Trevor" <trevor.bond at jcu.edu.au> wrote:
> >
> >> Large person SD = too few items.
> >> Bunching items is useful if you have a high stakes cut-point to use.
> >> Best
> >> T
> >> 
> >> 
> >> On 21/07/11 8:48 PM, "Michael Lamport Commons" <commons at tiac.net> wrote:
> >> 
> >>> Dear List Members:
> >> 
> >> What are the disadvantages and advantages of having the
> >>> Rasch item scores bunched up with a small S.D. versus spread out for items to
> >>> measure depression?  There person Rasch score have a very large S.D. which
> >>> indicates that the items are capturing a wide range of depression
> >> 
> >> 
> >> 
> >> My
> >>> Best,
> >> 
> >> Michael Lamport Commons, Ph.D.
> >> Assistant Clinical Professor
> >> 
> >> Department
> >>> of Psychiatry
> >> Harvard Medical School
> >> Beth Israel Deaconess Medical Center
> >> 234
> >>> Huron Avenue
> >> Cambridge, MA 02138-1328
> >> 
> >> Telephone (617) 497-5270
> >> Facsimile
> >>> (617) 491-5270
> >> Cellular (617)
> >>> 320­0896
> >> Commons at tiac.net
> >> http://dareassociation.org/
> >> ________________________
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> >u
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> >
> >
> 
> 
> My Best,
> 
> Michael Lamport Commons, Ph.D.
> Assistant Clinical Professor
> 
> Department of Psychiatry
> Harvard Medical School
> Beth Israel Deaconess Medical Center
> 234 Huron Avenue
> Cambridge, MA 02138-1328
> 
> Telephone (617) 497-5270
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