PubMed · 13336391
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R R POLLINI, M BREUSA. [Quartzite].. https://pubmed.ncbi.nlm.nih.gov/13336391/
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Various R(2) statistics have been proposed for logistic regression to quantify the extent to which the binary response can be predicted by a given logistic regression model and covariates. We study the asymptotic properties of three popular variance-based R(2) statistics. We find that two variance-based R(2) statistics, the sum of squares and the squared Pearson correlation, have identical asymptotic distribution whereas the third one, Gini's concentration measure, has a different asymptotic behaviour and may overstate the predictivity of the model and covariates when the model is mis-specified. Our result not only provides a theoretical basis for the findings in previous empirical and numerical work, but also leads to asymptotic confidence intervals. Statistical variability can then be taken into account when assessing the predictive value of a logistic regression model.
PURPOSE: To determine the change in compliance with the Royal College of Ophthalmologists biometry guidelines since the last National Audit 2 years ago and in particular to quantify the adoption of modern methods of axial length measurement and customization of A constants. METHOD: A structured telephone questionnaire of individuals who perform biometry in all eye departments in the United Kingdom. RESULTS: A biometrist was interviewed in 94 of the 178 United Kingdom Ophthalmology departments. Compared with 2 years ago, nurses alone perform biometry more frequently (67 vs 51%) and junior doctors less frequently (9 vs 15%). More biometrists now attend external training courses (45 vs 37%). The Royal College of Ophthalmologists recommended intraocular lens calculation formulae (SRK-T, Hoffer Q, and Holladay) are used more commonly (30 and 15%) and audit of prediction error is being performed more frequently (78 vs 71%). The routine use of a partial coherence laser interferometry has increased from 35 to 61% in United Kingdom Ophthalmology departments. Currently, only one United Kingdom department is routinely using immersion ultrasound biometry. 'A' constants are customized in 47% of departments. CONCLUSION: Over the last 2 years, there has been improved implementation of the Royal College of Ophthalmologists guidelines on biometry. It is essential that the Royal College of Ophthalmologists guidelines are updated to include current best practice of routine use of partial coherence laser interferometry or immersion biometry and customization of A constants. A benchmark standard of 85-90% of patients achieving a final postoperative refraction within 1 dioptre of the predicted should be established.
In 1995, a disease control and intervention project was initiated in Malmöhus county in southern Sweden to limit the spread of penicillin-resistant pneumococci. Since most of the carriers of pneumococci are preschool children, and since most of the spread is believed to take place in day-care, a mathematical model, in the form of a stochastic process, for the spread in a day-care group was constructed. Effects of seasonal variation and size of the day-care group were particularly considered. The model was then used for comparing results from computer simulations without and with intervention. Results indicate that intervention is highly effective in day-care groups with more than ten children during the second half of the year.