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Use of repertory grids
in quality control |
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The
processes used to assess the quality of
manufactured goods, and to prevent the production of faulty products,
are, one
imagines, unproblematic. After all, manufactured goods are physical
objects
whose required dimensions, weight, etc. can surely be specified in
straightforward objective terms. Vehicle
cylinder heads can be machined ‘to the nearest thou’ (thousandth of an
inch)
using a laser-controlled lathe; cardboard boxes filled with cornflakes
by
machinery that operates to the nearest hundredth of a gram. Personal
judgement,
one imagines, simply isn’t involved.
There
are, however, many processes which
are not as straightforward, and in which a surprising degree of expert
judgement is required. The ‘finish’ of a garment is one example. The
consistent
mixture of differing types and grades of tea-leaf according to the
seasonal
availability of entirely different leaves in order to produce the same
taste,
consistently each time, is another. Typically, these judgements are
made by
experienced employees who may not be able to articulate the logic
underpinning
their judgements beyond a simple assertion that they know when they’ve
got it
right: ‘It feels good to me’ or ‘it isn’t right’ being typical
statements.
One
can assess the accuracy of these kinds
of judgement very straightforwardly: when correct, the customer doesn’t
complain, and when incorrect judgements have been made, the goods are
returned
and the customer complains. The real problem arises when one wishes to
improve
quality control accuracy, and particularly, when one wishes to train
new
controllers to replace staff who are leaving. One needs a device for
making
tacit knowledge explicit (Jankowicz 2001).
To
what should the novice quality
controller learn to attend? What, exactly, is meant by the ‘finish’ of
a
garment? Is it the precision with which button-holes have been stitched
and the
care with which buttons have been sewn on? Or is it rather, the feel of
the
material as it’s rubbed between the thumb and the forefinger, or put to
the
operator’s cheek? And in the latter case, what should the nature of the
sensation be in the case of silk which has been woven properly or with
faults
during the process? Does it differ in the case of cotton, this
distinction
between the successful and unsuccessful weave? What constitutes
‘seconds’?
The
repertory
grid can be used to answer
questions like these. A dozen elements,
each being a physical sample of the
product, the whole set varying in overall quality as determined by the
experienced quality controller, is used. Elements are presented in
triads and
the controller is asked to indicate "in what way are two of these the
same, and
one different, in terms of quality? What exactly is it about them that
makes
you say that? What are you noticing, and how are you noticing it?"
The
answers are in the form of constructs,
the implicit pole
being identified with as much care as the emergent
pole to
identify the nature of both ends of the quality scale. A set of
constructs can
be obtained from several quality controllers and aggregated or
compared. The
attributes which are particularly characteristic of a well-finished
garment can
be pointed to, and the specific faults which must be identified during
the
quality inspection demonstrated to the novice quality controller. Or,
indeed,
the exact faults to be avoided during initial manufacture can form part
of the
training of the operatives who produce the product in the first place,
as part
of a detailed task analysis of the job itself. |
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References
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- Jankowicz, A.D. (2001). Why does
subjectivity make us nervous? Making the tacit explicit. Journal
of Intellectual Capital 2, 1, 61-73.
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Devi Jankowicz
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