Survival analysis is concerned with modelling the time before subjects change state, typically time until death or failure. One key feature of such data is that they can be censored, that is, some subjects will not have changed state before the study ends.

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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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1answer
36 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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24 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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Statistical analysis of time to event data

If I have 2 events of interest, lets say $X$ and $Y$. I would like to know, what is the influence of $Y$ on $X$. It's like a correlation between 2 events, but I'm not sure what is the formal test for ...
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How to determine if the occurrence of two events is temporally connected?

I'm working on a dataset where I have dates as the main unit of analysis. I'm trying to see if two events are related; that is, if the first event happens, will the second event happen within a month ...
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Measuring length of intervention effect

I ran a study in which participants were randomized to either a control or an intervention, with outcomes in the form of time-to-event data. While overall time-to-event is shorter in the intervention ...
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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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1answer
29 views

Hazard function for proportional odds model

The Cox proportional hazards model for survival data with covariate ${\bf z}$ is defined through the hazard function $h(t,{\bf z})$ by $$ h(t,{\bf z}) = h_0(t)~\cdot\theta~~,~~~\theta = \theta(\beta, ...
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Test for paired right censored data

I have a paired right censored data eg. ...
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157 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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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
28 views

Parametric distribution for time to event data - where event is 'uncertain'

Is there a canonical approach to deal with the modeling of time to event ($A$) where $P(A) \ne 1$. For instance, assume the marriage rate is 50%. The study is a set of times (ages) until marriage ...
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Using nonstationary independent variables in a panel survival model

I am debating with someone over the appropriate use of time series variables in a survival model. We have an unbalanced panel with a survival outcome (0,1), time-invariant features of the panel units, ...
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47 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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1answer
46 views

Difference between Kaplan Meier Estimator and the Empirical CDF

In survival analysis, you often use the nonparametric maximum likelihood estimator (i.e. Kaplan-Meier estimator) of the survival function $S(t)$. Since $S(t) = 1 - F(t)$, shouldn't we also be able to ...
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96 views

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
54 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
41 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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34 views

Can I use survival analysis to model employee attrition when employees have different start dates?

I have a dataset of a few thousand employees and want to compare time-to-terminate by their source of hire. The data is for a four year period. Out of the dataset about 15% have terminated, while the ...
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1answer
33 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

Confidence intervals of fitted Weibull survival function?

I'm implementing a Weibull survival analysis fitter, and have successfully estimated the parameters and their standard errors. I can also produce the fitted survival curve. My question is how can I ...
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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
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Person-time still contributed after censorship? (Stata)

I feel like I might be going a little crazy here, so I'd appreciate some advice. I have a multiple-record-per-subject dataset that goes something like this: id | day | failure ----+------+-------- ...
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1answer
213 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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Relationship between Gumbel and Weibull distribution, accelerated failure time models, and Survreg using R

I have three questions concerning accelerated failure time models (AFT), one statistical, one regarding how to implement these models in R, and one related to finding out information about what R is ...
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55 views

Finding significant predictors of psychiatric readmissions

The set of data I am working contains nearly 17,000 independent spells (each spell consists of a number of hospital episodes) each belonging to a unique patient ID. I have spent a very long time ...
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How to tell the probability of failure if there were no failures?

I was wondering if there is a way to tell the probability of something failing (a product) if we have 100,000 products in the field for 1 year and with no failures? What is the probability that one of ...
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How to show that the cumulative hazard function is equal to the formula below?

I need help to show the equation below. $$H(t)=ln[\frac{mrl(t)}{mrl(0)}]+\int_{0}^{t}\frac{1}{mrl(u)}du$$ where mrl is the mean residual life using $$h(t)=\frac{\frac{d}{dt}mrl(t)+1}{mrl(t)}$$
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22 views

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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For the survival analysis package in R, what is the log-likelihood of “survreg( Surv(time, censor) ~ age, dist=”exponential“)”?

I am currently trying to read through examples from http://www.ats.ucla.edu/stat/r/examples/asa/asa_ch1_r.htm. One of the models I saw was: ...
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1answer
65 views

ML estimate of exponential distribution (with censored data)

In Survival Analysis, you assume the survival time of a r.v. $X_i$ to be exponentially distributed. Considering now that I have $x_1,\dots,x_n$ "outcomes" of i.i.d r.v.'s $X_i$. Only some proportion ...
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Application of Survival Analysis

The question is whether prenatal diagnosis of a congenital condition shortens the time to surgical intervention. The condition is one that is obvious at birth, but not necessarily in utero, and once ...
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75 views

How to calculate probabilities when there is censoring?

Suppose we have 10 patients among whom 4 readmit and 2 get censored. Then what is the probability of readmission of these patients? My intuition tells me it should be 0.5, because I couldn't observe ...
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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
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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1answer
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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1answer
86 views

Expected survival time from log-logistic survival model in R from survreg

I'm currently estimating a survival model (accelerated failure time model) with a log-logistic distribution in R using the survival package and the survreg function. I want to simulate expected ...
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Estimating mortality rates with direct age-standardization

I'm attempting to calculate the mortality rates of AMI (acute myocardial infarction) in patients (cases) with high bloodpressure, between the years 2001 to 2008. For every case I have 2 matched ...
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Modelling mortality rates using Poisson regression

I'm examining trends (between 1998 and 2011) in mortality rates among patients with Crohn's disease. Each patient (case) have been included during 1998 to 2011. At inclusion, each patient have been ...
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1answer
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Is there any repository with interval censored time-to-event datasets?

I'm looking for this particular structure of data for working on my thesis. In particular, I need interval censored with a cure fraction data. This kind is actually popular in medicine and clinical ...
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1answer
28 views

What Grouping Method To Determine Average Over Lifetime?

I have the following data: When individual 'x' joined a company. As the data is limited to 2 years I do not know the start date of every individual. When individual 'x' left the same company. If this ...
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2answers
146 views

How to make prediction in survival analysis using R?

I have fitted a survival model in R which is below. However, I am not sure how to make predictions. I tried predicting the survival probability that a patient whose design matrix is ...
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How to compare repeated measurements among groups with non-normal data?

I want to investigate differences in two variables among 3 groups. The variables are "% of time active" and "latency to exit a cage", and each group corresponds to a different context (the focal ...
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Confidence interval before the first event in a Kaplan–Meier curve

The confidence intervals for Kaplan–Meier curves in survival analysis only exist for times after the first (non-censored) event. Example R code: ...
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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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Model selection using AIC in Survival Analysis

As far as I know, the model with lowest AIC is said to be better. However, according to the R output below, the writer says, the model called wei is better, whose ...
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1answer
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Why are the signs of my coefficients are different?

My code is: library(survival) attach(veteran) survreg(Surv(time,status)~karno+diagtime+age+prior+trt ,dist="w") My analysis and the one in a book are as follows: ...
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1answer
54 views

How to interpret a status other than alive or dead in data for survival analysis?

I am working on a famous data set from this book. The data set consists of measurements on 418 patients. I am interested on modelling the variable; futime: number of days between registration ...