BACKGROUND Polytomous logistic regression models are commonly used in case-control studies of cancer to directly compare the risks associated with an exposure variable across multiple cancer subtypes. However, the validity, accuracy, and efficiency of this approach for prospective cohort studies have not been formally evaluated. METHODS We investigated the performance of the polytomous logist...

In clinical trials conducted over several data collection centers, the most common statistically defensible analytic method, a stratified Cox model analysis, suffers from two important defects. First, identification of units that are outlying with respect to the baseline hazard is awkward since this hazard is implicit (rather than explicit) in the Cox partial likelihood. Second (and more seriou...

BACKGROUND High cyclooxygenase (COX)-2 expression in ovarian tumors has been associated with poor prognosis, but the role of COX-1 expression and its relation to survival is less clear. Here, we evaluated COX expression and associations with survival outcomes between type I (clear cell, mucinous, low grade endometrioid and low grade serous) and type II (high grade serous and high grade endometr...

background the aim of this study was to examine the impacts of multiple indicators of socio-economic status (ses) on congestive heart failure (chf) related readmission.   methods a prospective study consisting of 315 patients without the history of admission due to chf was carried out in tehran during 2010 and 2011. they were classified into quartiles based on their ses applying principal compo...

Stratified Cox regression models with large number of strata and small stratum size are useful in many settings, including matched case-control family studies. In the presence of measurement error in covariates and a large number of strata, we show that extensions of existing methods fail either to reduce the bias or to correct the bias under nonsymmetric distributions of the true covariate or ...

Many data sets used by economists and other social scientists are collected by stratified sampling. The sampling scheme used to collect the data induces a probability distribution on the observed sample that differs from the target or underlying distribution for which inference is to be made. If this effect is not taken into account, subsequent statistical inference can be seriously biased. Thi...

OBJECTIVE Evaluate differences in TB outcomes among different provider types in Chicago, IL. METHODS We retrospectively reviewed all TB cases reported to the Chicago Department of Public Health (CDPH) from 2008 through 2011. Provider type was stratified into three groups: public, public-private, and private providers. Multivariate regression was used to evaluate treatment duration and time to...