[Cox proportional hazards regression][1] is a very popular, semi-parametric method for survival analysis.

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Paired homogeneity test: Compare two regression coefficients in R

I have a question about paired homogeneity test. By using Cox regression analysis Im evaluating 2 new biomarkers (A and B) in association with a outcome (X). I developed 2 multivariable models and on ...
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R Packages for rank-preserving structural failure time model (RPSTM)

I have a randomized clinical trial data that has high percentage(30-40% in both arms) switching over to a different treatment regimen. By browsing through some literature, I am inclined to perform ...
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Heterogeneity test for risk factor association (hazard ratio/coefficient) in two or more different survival outcomes

Suppose I'm interested in comparing smoking category (current, ex, non-smoker) as a risk factor in two or more different but similar (considerably exclusive) outcomes, say lung cancer of different ...
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38 views

Calculating Sample Size for Non-Inferiority Test in Cox Proportional Hazards Regression With Stratification

I have a binary predictor, X, in a Cox proportional hazards regression model, and I want to show that it is NOT a significant predictor. In other words, I want to show that there is not a significant ...
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25 views

Determining sample size for proportional hazard

I am in the design phase for a longitudinal study examining the effect of a predictor (neighborhood risk score) on time to an outcome (re-arrest), as well as whether or not the variation explained by ...
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Odds ratio of a continuous variable (univariate cox proportional hazards), how to plot that variable against death%?

I have a continuous variable X with which i ran Cox proportional hazards. The outcome was 1=Death, 0=censored/stillalive. I have an odds ratio 0.516 for this predictor. 1) How do i interpret that ...
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12 views

What estimator to use in Cox model

I am using R/survival to analyze survival data from cancer patients. I have recently learned that there are many kinds of estimators for the Cox model, and I understand, that in theory, their order of ...
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158 views

A peer-reviewer wants more complex statistical modeling - is it reasonable?

I've submitted a manuscript to a journal and the associate editor wrote that his readers will want to know more about how the predictor of main interest (occupation) is related to death, and this will ...
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52 views

Overfitted Cox regression

I'm trying to compare the prediction abilities for death of two new biomarkers using a cohort of 173 patients. My problem is that I have only 31 outcomes and my baseline model (the one without any ...
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15 views

Cox Regression Analysis

I am trying to model the inter-arrival time between events as a survival model that depends on a set of covariates. So, I treat each event as a "death" in my model and therefore, calculate the ...
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1answer
49 views

Interpretation of interaction between covariates and time in cox regression

If I have a categorial variable (let's say $X$) and a continuos variable (let's say $Y$). IF I fitted a standard cox model, it will result in a violation of the constant HR over time (based of ...
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Is there a way to model left truncated and interval censored data in R or SAS?

We have a study where our participant underwent some surgery at time = 0, but at various ages. Our follow-up is based only on Medicare age-eligible people, so we have to wait until they reach the age ...
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1answer
55 views

Average hazard rate with Cox proportional hazard model always larger than the hazard rate without any explanatory variables?

I am estimating a Cox proportional hazard model with and without explanatory variables. Without explanatory variables, the hazard rate is just the proportion of all individuals that failed at time ...
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1answer
24 views

Is Cox PH model still applicable when proportional assumption is violated for treatment effect?

I am using Cox proportional hazard model to compare the survival of two groups (treatment vs control) of patients. However, hazard rates were not proportional between the groups. Now, would it make ...
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1answer
43 views

Extrapolating the effect of covariable changes in Cox proportional hazards models

I have a Cox proportional hazards model in R (see made-up example below) that models the effect of some variable, say weight. From this model, I'd like to extrapolate what a change in weight from say ...
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1answer
34 views

Interpretation of Cox regression with time varying covariates

After fitting my model to a time varying cox regression, let's say I have a continuos variable $ X $. The hazard ratio of this variable will be higher than 1 (about 2 and it is significantly ...
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27 views

Can the rcorrp.cens paired concordance test be done taking into account strata?

Followup to these discussions: Bootstrapping Hmisc::rcorrp.cens for paired concordance? Stratified concordance index (survival::survConcordance) Is there a way to perform a stratified paired ...
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1answer
216 views

How to create a toy survival (time to event) data with right censoring

I wish to create a toy survival (time to event) data which is right censored and follows some distribution with proportional hazards and constant baseline hazard. I created the data as follows, but I ...
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50 views

AIC or BIC for model selection in Cox regression (SPSS)

Does anyone know if there is a method (a macro) to calculate AIC or BIC for a model in Cox regression using SPSS?
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Stratified concordance index (survival::survConcordance)

What is the idea of having a stratified concordance (C-index) in survival::survConcordance, as opposed to computing the concordance over all samples ignoring the strata? Can there be some inflation ...
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Is the magnitude of the hazard ratio change reflective of survival function change?

I need to know the change in survival caused by increasing inbreeding in my study group. As my model has random effects, and as coxme has no easy ...
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1answer
62 views

How to conduct Cox PH stratisified by matched pair in R

I am wanting to calculate hazard ratio in a matched cohort design. For such I am using the coxph() function in R. But I have been recommended to stratify by matched ...
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heteroskedasticity in logit/cox

I am using a logit and a cox proportional hazard model for my analysis, and the newest version of Stata. I have found that there are no tests to check for heteroskedasticity for logit/probit models, ...
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56 views

Interpreting output of Cox regression model

I am trying to use two variables - activity score (ascore - a whole number indicating amount of activity) and gini (given by Gini-Simpson index - a value ranging between 0 and 1, indicating diversity ...
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How can the output from a Cox proportional hazards model be mathematically translated into a log regression model? [closed]

I would like to write down the log-regression model associated with the formula: coxph(Surv(time, status) ~ rx + cluster(litter), rats) I am not interested in ...
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41 views

Study design - fresh look!

Need to be advised outside of the circle. I am more a physiologist+mathematician plus-c,c++,java coder/developer. Chart data. From year 2001 till 2012. 89 nursing stations or emergency call ...
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Change in destribution af variable with time - doing cox regression

A hopefully a question that has a simple answer:) I'm doing cox regression on a large dataset. Event=death. Destribution of the main variable change a lot during the timespand (10years) - i.e type of ...
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calculus of predicted number of failures in cox regression

Suppose we rank the prognosis index (the linear product beta*X) of the individuals in a Cox regression and divide this set in a number G of groups. It is trivial to count the number of observed ...
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how to deal with dependence/interaction among covariates in a cox regression model

In case of a linear regression, if we are to account for interaction between two regressors x1 and x2, we write a model like ...
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1answer
94 views

Is oversampling done for Cox regression data?

I have a dataset consisting of about 48000 people, about 40,000 of which die before the end of the study and get a failed = 1 and the remaining 8000 have a failed = 0 because they're either lost to ...
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39 views

Cox PH model - Time-independent vs time-dependent covariates

I am trying to fit two different Cox PH models to some data I have, and get strange results when I consider the same variable as time-independent as opposed to when I consider it time-dependent. More ...
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124 views

Cox discrete time regression model question

Cox's 1972 publication Regression Models and Life Tables links logistic regression to an extension of the discrete time proportional hazard model. I do not understand how Equation (21) in the ...
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Is it possible to gain point survival estimates from a coxme object?

I have a coxme object: (Age, status) ~ F + X1 + X2 + (1|R1) + (1|R2) + (1|R3) Where F is an individual's level of inbreeding, X1 ...
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Model Selection with Competing risks in Cox regression

When doing cox proportional hazards regression one often has competing risks. The typical approach for this is to fit separate cox proportional hazards models for each risk, censoring the competing ...
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R adds unexpected variable to interaction model

Not sure if this is more of a programming question (in which case please move to stack overflow) or a statistical model question (in which case, please read on!) I'm exploring a data set and doing ...
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28 views

Study Length Over-Estimating Hazard Ratio?

Are cox model studies over too long a time-scale at risk of over estimating (or under estimating) a covariate's effect on hazard? I'm studying inbreeding in a captive animal population. Some ...
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106 views

Survival analysis for matched set cohort data - Methods for absolute and relative risks?

BACKGROUND I have a matched data set with 10,000 cases and 20,000 controls. Cases are defined as such due to a diagnosis of COPD (Chronic Obstructive Pulmonary Disease - a lung disease caused by ...
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118 views

Survival Analysis on Telecom Churn in R

I am working on Telecom Churn problem and here is my dataset. http://www.sgi.com/tech/mlc/db/churn.data Names - http://www.sgi.com/tech/mlc/db/churn.names I'm new to survival analysis.Given the ...
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114 views

Prediction with categorical variables in Cox regression

I'm doing survival analysis with Cox PH. I have my final model based on averaged models and I have four categorical variables with multiple levels each. I computed the fitted values using ...
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Cox Models treatments depending on time until event

I'm trying to get the "productivity" of treatments like sending an email, calling or sending an SMS and their combinations in the paying debtor's probability. I couldn't find one model that satisfies ...
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Violation of Cox Proportional Hazards by a continuous variable

[This question is related to 1 and 2 on this site.] I fit a Cox model with these three time dependent variables: {s:numeric, C:binary, l:numeric }. I have 1069 ...
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Akaike information criterion for Cox proportional hazard models

I am conducting an analysis of survival data using Cox proportional hazard (CPH) models, to figure out what is the best model to use. The models I am comparing are non-nested. My plan is to compute ...
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How can parameter expansion be applied to cox proportional hazard models with random effects?

Parameter expansion is used in various GLMMs to accelerate e.g. EM or Gibbs convergence. Is anybody aware of a paper/work which implements PX for CPH?
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Cox proportional hazards (setting a reference level and an interaction with time)

I am currently trying to analysis some data in R using Cox proportional hazards. I have been able to get my coxph model to run but, I am having some coding difficulties. I have two factors (individual ...
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44 views

Discrepancy between Kaplan-Meier curves and Cox Model

I have plotted Kaplan-Meier curves of survival times for cancer patients with above and below average levels of Copy Number Variation (CNV), and performed a log-rank test for each cancer type. I have ...
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4answers
165 views

Determine where hazards starts to increase for a continuous variable

I'm interested in a continuous variable, namely blood pressure. The higher the blood pressure, the greater the risk of heart attack and stroke. However, studies frequently report that also low blood ...
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Relating the effect of a composite variable to multiple causative variables

I have the following scenario: I am measuring Copy Number Variation (CNV) in various types of cancer. To explain: the genome is essentially like one long sentence, with genes as words, and each cell ...
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How do I report the data from a Cox proportional hazard regression model on SPSS

I was just wondering if there is a set way to write the results within a CPH model, I have obtained results from SPSS and I have values for Sig B and the 95% Confidence interval. What I am after is ...
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Approximating cox model with time varying covariates using poisson

How do you reformat a dataset in order to perform a cox regression with time-varying covariates as a poisson regression. I'm trying to run a survival analysis regression in python with time varying ...
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How to assess the functional form of covariates in the Cox model with martingale residuals in R?

I want to find if the functional forms of covariates in my Cox model are linear. I understand the way to do this is to plot the Martingale residuals against the covariate of interest. I have found ...