Statistics in medicine
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Statistics in medicine · Jul 2007
Modelling seasonal and weather dependency of cardiac arrests using the covariate order method.
A data set concerning cardiac arrests treated by the Emergency Medical Service in Trondheim during a nine year period is analysed. The relationship between the occurrence of cardiac arrest and covariates related to weather and season is examined. The covariate order method is used in the analysis of the data. ⋯ The incidence of cardiac arrest decreases with increasing temperature. Further a significant effect of snowfall is also found, with increased intensity of cardiac arrest on days with snowfall. A more borderline significant effect of precipitation is also identified.
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Statistics in medicine · Jul 2007
The performance of different propensity score methods for estimating marginal odds ratios.
The propensity score which is the probability of exposure to a specific treatment conditional on observed variables. Conditioning on the propensity score results in unbiased estimation of the expected difference in observed responses to two treatments. In the medical literature, propensity score methods are frequently used for estimating odds ratios. ⋯ Stratifying on the propensity score resulted in moderate bias, with relative biases ranging from 15.8 to 59.2 per cent. For both methods, relative bias was proportional to the true odds ratio. Finally, matching on the propensity score tended to result in estimators with the lowest MSE.