# [Rasch] qualitatively described, quantitatively responded

Agustin Tristan ici_kalt at yahoo.com
Wed Nov 7 10:38:20 EST 2007

```Hello Shirin:
It is clear that the use of nominal categories (eventually ordinal) doesn't permit to make calculations, so likert scales and other rating scales transform ordinal scales into numbers. Using the Rasch-Andrich model for rating scale you can transform these numbers into something more suitable.
In fact when you say that the scale is from 1-9 because you have 9 ordinal categories, it doesn't means that you have a distance of "1" unit between the names of the categories, but the model helps to transform into meaningful measures, so you may see the relative distance among categories.
Is it better 9 than 3? it depends on what you wish to show, but probably 9 is too much (7 +/- 2 is the magical number), as it is difficult to differentiate between categories.
Once you have a meaning of the measures, proceed on reverse direction, try to identify the construct involved with the positions on the scale and define from less to more the best suitable names, but not only: poor, medium, good, excellent and so forth, but include a description, such as:
a) excellent is able to write phrases with a correct syntax, make interpretacions, propose conclusions, etc.
...
b) poor is able to write incoherent phrases, bad use of construction rules, etc.
hope this helps

shirin shirazi <shirin71_shirazi at hotmail.com> wrote:
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Hi

I have thirty essays to rate. There is a rating scale consisting of nine descriptors. The first one describes the writing ability of the writer as a "fully competent". If the writer suits this level, he gets nine. If he adequately responds to the task, it brings him down to eight and the same process continues up until zero where there is no response to the task. I wonder how these numbers have been given to these qualitative words. Fully 9, adequately 8, to some extent 7, partially 6, ...

The second question is that why do we have a range of descriptors from nine (at most) to three (at least)?

Third why don't we have qualitative words to describe levels of performance since descriptors are describing the proficiency in qualitative manner, for example instead of earning a 9 in IELTS, we allocate a word such as competent or incompetent or effective or ineffective which are in harmony with qualitative words appearing in descriptors. Do we use numbers since they are more tangible (People come to grips with them easily)?

Best
Shirin

---------------------------------
Date: Mon, 5 Nov 2007 15:43:55 -0800
From: ici_kalt at yahoo.com
Subject: Re: [Rasch] qualitatively described, quantitatively responded
To: shirin71_shirazi at hotmail.com

hello! what is exactly the problem you are trying to solve? describe your test please.
regards
agustin tristan

shirin ahmadishirazi <shirin71_shirazi at hotmail.com> wrote:
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Hi List members,

I would be extremely grateful if you help solve the following controversies:

1. Qualitative words are not appropriate to describe a quantitative construct.
2. Qualitative words are used to differentiate descriptors of levels of proficiency (although it is difficult to make distinctions between "some" and "a few", and "several" and "many").
3. Productive skills (Speaking and writing) are qualitatively described but quantitatively scored. How can qualitative words (e.g., fully, sufficiently, partially, minimally, largely, adequately, effectively, ...) get quantified?

All the Best,
Shirin

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