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SUMMARY:Applying principles of item response theory to produce efficient u
 ltra-short form questionnaires - Prof. Mark Haggard\, Department of Psycho
 logy\, University of Cambridge
DTSTART:20130212T163000Z
DTEND:20130212T173000Z
UID:TALK42777@talks.cam.ac.uk
CONTACT:Luning Sun
DESCRIPTION:Efficient development of ultra-short form questionnaires (3 or
  4 items\, eg for clinical use) is worth pushing to its limits. Success wo
 uld discourage non-standardised use of similar questions in unconsidered i
 nterview format\, and discourage the fantasy that single question response
 s can be taken precisely at face value\, while acknowledging that lengthy 
 questionnaires are often impractical. Factorial purity (‘consistency’ 
 given by Cronbach’s alpha) has long been the overriding process goal for
  item selection and final performance indication\, but it deserts us as a 
 quality guarantor whenever we seek an intrinsically heterogeneous summary 
 measure\, or seek a pattern of discrimination that is not for linear predi
 ction of a continuous measure but for a non-linear criterion such as an ex
 treme cut-off (dichotomy). It is not necessary to reach the ideal of Rasch
  measurement\, where (a few) items have to be highly selected\, and once a
 n item’s response curve has been appropriately located on the scale\, it
  does most of the discriminatory work in that portion of the scale. But it
  is possible\, with appropriate cautions about reliability and validity\, 
 to meet the general development objective with (1) an additive linear mode
 l using available items of overlapping response and heterogeneous response
  slope\, and (2) emphasis on metrical validity\, adding this to the classi
 cal 4 types of validity (face\, construct\, criterion\, ecological). We se
 e an index of validity of any of the 5 types as a goal to be sought throug
 h all stages in the psychometric process\, not just a final performance in
 dicator justifying adoption and use\, according to some conventional cut-o
 ff. Combining these two approaches entails pursuing and optimising item sc
 aling through several stages.  Where the properties of the final criterion
  measure are clearly understood\, item choice\, item scaling and total sco
 re formulation can all be done to optimise for a particular application in
  view. These points are illustrated on a piece of applied development work
  in health status measurement meeting an outside request for a short-form 
 measure using items in a clinical trial database. Two reasonable and relat
 ed development criteria recognised by the field were adopted\, but it was 
 found that the distributional and linearity constraints that measures for 
 the two criteria required were radically different. Proper consideration o
 f metrical validity led to us offering two ultra-short forms\, one for eac
 h of the criteria adopted\; though conceptually related\, these criteria w
 ere metrically irreconcilable. As often with consulting\, the user’s req
 uirement was redefined (ie as two)\, partly by problem analysis\, but also
  by the fine-structure of the data.
LOCATION:Seminar Room\, Department of Psychology\, Downing Site\, Cambridg
 e
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