Publications by Christos Argyropoulos
Survival Analysis With Generalized Additive Models : Part IV (the survival function)
The ability of PGAMs to estimate the log-baseline hazard rate, endows them with the capability to be used as smooth alternatives to the Kaplan Meier curve. If we assume for the shake of simplicity that there are no proportional co-variates in the PGAM regression, then the quantity modeled corresponds to the log-hazard of the survival function...
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Survival Analysis With Generalized Additive Models: Part V (stratified baseline hazards)
In the fifth part of this series we will examine the capabilities of Poisson GAMs to stratify the baseline hazard for survival analysis. In a stratified Cox model, the baseline hazard is not the same for all individuals in the study. Rather, it is assumed that the baseline hazard may differ between members of groups, even though it will be th...
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Empirical bias analysis of random effects predictions in linear and logistic mixed model regression
In the first technical post in this series, I conducted a numerical investigation of the biasedness of random effect predictions in generalized linear mixed models (GLMM), such as the ones used in the Surgeon Scorecard, I decided to undertake two explorations: firstly, the behavior of these estimates as more and more data are gathered for each i...
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The little mixed model that could, but shouldn’t be used to score surgical performance
The Surgeon Scorecard Two weeks ago, the world of medical journalism was rocked by the public release of ProPublica’s Surgeon Scorecard. In this project ProPublica “calculated death and complication rates for surgeons performing one of eight elective procedures in Medicare, carefully adjusting for differences in patient health, age and hospit...
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Estimating the mean and standard deviation from the median and the range
While preparing the data for a meta-analysis, I run into the problem that a few of my sources did not report the outcome of interest as means and standard deviations, but rather as medians and range of values. After looking around, I found this interesting paper which derived (and validated through simple simulations), simple formulas that can b...
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Sequential Fitting Strategies For Models of short RNA Sequencing Data
After a (really long!) hiatus I am reactivating my statistical blog. The first article concerns the clarification of a point made in the manual of our recently published statistical model for short RNA sequencing data. The background for this post, in case one wants to skip reading the manuscript (please do read it !), centers around the limi...
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