[Forum SIS] Bocconi DEC Seminar Elena Stanghellini - December 11th

[Marco Bonetti]

> DEC Seminar
> Università Bocconi,
> Room N10
> Piazza Sraffa 13 - 1st floor
> Time: 12:30pm
>
> The DEC seminar schedule is available at http://www.unibocconi.eu/statseminar
>
> Friday, December 11th
>
> Elena Stanghellini
> (Dipartimento di Economia Finanza e Statistica
> Università di Perugia)
>
> "Modelling health scores with the skew-normal distribution"
>
> Abstract:
>
> Health care interventions which use quality of life or health scores  
> often provide data which are skewed and bounded. The scores are  
> typically formed by adding up responses to a number of questions.  
> Different questions might have different weights, but the scores  
> will be bounded, and are often scaled to the range 0 to 100.
> If improvement in health over  time is measured, scores will tend to  
> cluster near the 'healthy' or 'good' boundary as time progresses,  
> leading to a skew distribution. Further, some  patients will drop  
> out as time progresses, so the scores reflect a selected population.
> We fit models based on the skew-normal distribution to data from a  
> randomised controlled trial of treatments for sprained ankles, in  
> which scores were recorded at baseline and 1, 3 and 9 months. We  
> consider the extent to which skewness in the data can be explained  
> by the clustering at the boundary via a comparison between
> a censored normal and a censored skew-normal model.
> As this analysis is based on the complete data only, a formula for  
> the distortion of the treatment effects due to informative drop-out  
> is given. This allows us to assess under which conditions the  
> conclusions drawn on the complete data may be either reinforced or  
> reversed, when the informative drop-out process is taken into account.
>

---
Marco Bonetti
Department of Decision Sciences
Bocconi University
Via Guglielmo Roentgen 1
20136 Milan, Italy
Tel +39 02 58365670
Fax +39 02 58365634

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