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- Harley, M, et al.
(författare)
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Was Rodney Ledward a statistical outlier? Retrospective analysis using hospital data to identify gynaecologists performance
- 2005
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Ingår i: British Medical Journal, 2005, 330, 929.
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To investigate whether routinely collected data from hospital episode statistics could be used to identify the gynaecologist Rodney Ledward, who was suspended in 1966 and was the subject of the Ritchie inquiry into quality and practice within the NHS. Design A mixed scanning approach was used to identify seven variables from hospital episode statistics that were likely to be associated with potentially poor performance. A blinded multivariate analysis was undertaken to determine the distance (known as the Mahalanobis distance) in the seven indicator multidimensional space that each consultant was from the average consultant in each year. The change in Mahalanobis distance over time was also investigated by using a mixed effects model. Setting: NHS hospital trusts in two English regions, in the five years from 1991-2 to 1995-6. Population: Gynaecology consultants (n = 143) and their hospital episode statistics data. Main outcome measure Whether Ledward was a statistical outlier at the 95% level. Results: The proportion of consultants who were outliers in any one year (at the 95% significance level) ranged from 9% to 20%. Ledward appeared as an outlier in three of the five years. Our mixed effects (multi-year) model identified nine high outlier consultants, including Ledward. Conclusion: It was possible to identify Ledward as an outlier by using hospital episode statistics data. Although our method found other outlier consultants, we strongly caution that these outliers should not be overinterpreted as indicative of "poor" performance. Instead, a scientific search for a credible explanation should be undertaken, but this was outside the remit of our study. The set of indicators used means that cancer specialists, for example, are likely to have high values for several indicators, and the approach needs to be refined to deal with case mix variation. Even after allowing for that, the interpretation of outlier status is still as yet unclear. Further prospective evaluation of our method is warranted, but our overall approach may be potentially useful in other settings, especially where performance entails several indicator variables.
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| 3. |
- Azad, Abul Kalam, 1966, et al.
(författare)
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Electron doping effect on structural and magnetic phase transitions in Sr2-xNdxFeMoO6 double perovskites
- 2006
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 179:5, s. 1303-1311
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Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline Sr2−xNdxFeMoO6 (x=0.0, 0.1, 0.2, 0.4) materials have been synthesized by a citrate co-precipitation method and studied by neutron powder diffraction (NPD) and magnetization measurements. Rietveld analysis of the temperature-dependent NPD data shows that the compounds (x=0.0, 0.1, 0.2) crystallize in the tetragonal symmetry in the range 10–400 K and converts to cubic symmetry above 450 K. The unit cell volume increases with increasing Nd3+ concentration, which is an electronic effect in order to change the valence state of the B-site cations. Antisite defects at the Fe–Mo sublattice increases with the Nd3+ doping. The Curie temperature was increased from 430 K for x=0 to 443 K for x=0.4. The magnetic moment of the Fe-site decreases while the Mo-site moment increases with electron doping. The antiferromagnetic arrangement causes the system to show a net ferrimagnetic moment.
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