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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24 views

Incorporating interval-censored event times into standard survival models

I am trying to model the time until some event occurs for individuals observed over a 24 month period. For about 75% of people, no event occurs. For 15% of people, we know exact time of the event. ...
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26 views

Variance-covariance matrix of survival model

Suppose I have a survival model like this: ...
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8 views

Discrete time analysis - laying out the data

I have two time-varying covariates (Residence Status [1 = In Residence, 0 = not in residence], and cumulative GPA. I would like to incorporate these variables into my Excel sheet before importing it ...
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22 views

How to predict cumulative hazard in survival analysis?

Suppose I have a survival model like this: ...
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10 views

Using a Decision Tree Algorithm such as C4.5 to understand population Partition

I have multivariate data about a certain population with more than 1000 attributes per exemplar. Some of the variables are basic demographics attributes including: gender, age, race, ethnicity, ...
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25 views

Statistics of time dependent variable observable only at end-of-life, given survival data

I have a variable whose value I can only measure at the end-of-life of a product (which is not fixed). The variable's value, continuous and between 0 and 100, may be related to its age at that time. ...
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1answer
20 views

Inference with only left-censored data

Suppose I have a data set that is only left-censored data, ex: <5, <5, <5, <10, <10, <10 A technique to handle left-censored data is the Kaplan Meier estimate, see page 5 of ...
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1answer
30 views

Interaction in Survival analysis

I am a physician and clearly not a statistician (I try to understand why and how to perform the right analysis, but I don't understand the formulas). I am using SPSS v.19 in analyzing my data. I try ...
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2answers
51 views

How exactly can the Cox-model ignore exact times?

The Cox model does not depend on the times itself, instead it only needs an ordering of the events. How come it doesn't need the time, as all of the models I've seen so far are dependent on the exact ...
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16 views

Cormack Jolly Seber - remove capture histories of individuals only encounter at initial capture?

Considering that parameter estimations in a CJS model (detection probability and survival) are developed using a capture history observed after the first release, is it not appropriate to remove ...
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1answer
38 views

Is survival analysis suitable for this comparison?

I'm monitoring a website where I have two kinds of users (say, A and B). These users are able to contribute to this site in a variety of ways and, for each contribution, its time is logged. What I ...
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21 views

Time-scale in cox porportinal hazards model with multiple time-dependent variables

I'm doing survival analysis and I have three time-dependent variables, with different time scales each. I've already done univariate analysis and I want to proceed with multivariate analysis. My ...
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17 views

R Interpret coefficient from Survreg(dist=“gaussian”)

I was wondering if anyone could help me on how to interpret the coefficient from an analysis I have carried out in R (survival package). The data is right ...
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14 views

What is the diff between singly censored and progressive censored data in survival analysis?

I have a question regarding survival analysis . To my understanding, the singly censored data are those if there is one point in time, i.e, say, if the patient died (bulb is still working?) after ...
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17 views

Difference in Effect for Time-Varying Covariate in Survival Analysis

I am analyzing offender recidivism data using survival analysis. In particular, I am looking at the risk of getting arrested as a function of employment. When I treat employment as a time-varying ...
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3answers
160 views

Training, testing, validating in a survival analysis problem

I've been browsing various threads here, but I don't think my exact question is answered. I have a dataset of ~50,000 students and their time to dropout. I am going to be performing proportional ...
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0answers
14 views

Get values of survival function in SAS [migrated]

I generated a random sample from an exponential distribution and sorted them so they are going from lowest to highest value, giving me my order statistics. Now I need to get the values of the survival ...
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0answers
12 views

Converting a parametric survival model to a cash flow model. How do I account for aging in the population?

I'm building a survival model for time to failure of widgets. Other members of the team want to convert the model to a cost flow model. The basic idea is that we can use the functional form of the ...
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15 views

Is it possible to model BOTH censoring and truncation in BUGS?

Survival times are often right censored and left truncated. From my experience, it does not seem like OpenBUGS allows for both. Truncation is denoted as T( , ) and censoring as C( ,). For instance, a ...
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7 views

Specifying variance structure in mixed effects Cox model in R [migrated]

I am fitting a mixed effects Cox model in R using the function coxme() in the coxme package. In my model I have a censored survival time $X$, a single covariate ...
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2answers
36 views

How to interpret standard errors in a Cox model?

I am running a multi-variate Cox regression and Stata provides the standard errors for each hazard ratio. How are theses to be interpreted? I know that I want my coefficients to be large compared to ...
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33 views

Sample size / power calculation for logrank survival test

I have really little idea of survival analysis. I am aware that logrank is a special case of Cox' proportional hazards model, and that tons of R packages and scripts address the problem of power / ...
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0answers
10 views

Correlation between predictor variables and time in Survival Analysis?

I am using survival analysis to model time to an event. I would like to explore the effect of a continuous predictor variable on the hazard rate. The continuous predictor ranges in value from 0-8.5. ...
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46 views

Censored data prediction

I am working with the survivorship bias free database of hedge funds and trying to estimate the persistence of performance in the future performance of such funds based on the past performance. In ...
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6 views

Frailty conundrum: how can area effects be large when shared frailty variance for area is non-sig?

I’m running Cox proportional hazards models (in stata) to predict risk of teenage birth, where individuals (c. 50 000, c. 3000 births) are clustered within wards (>500). In null models with shared ...
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1answer
86 views

Obtaining a Probability Distribution From a Survival Function

Edit: I basically want to have a probability curve where a X value of 0.002 would be associated with a Probability of 1 and would also have data points of (0.005,0.1), (0.008,0) which is seen in the ...
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1answer
172 views

Bayesian Survival Analysis: please, write me a prior for Kaplan Meier!

Consider right-censored observations, with events at times $t_1, t_2, \dots$. The number of susceptible individuals at time $i$ is $n_i$, and the number of events at time $i$ is $d_i$. The ...
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21 views

Time varying predictors at higher aggregation levels in multilevel survival analysis

The case: I am trying to estimate event history models (also known as survival models) with time-varying predictors at two different levels of (geographical) aggregation. More precisely, I am using a ...
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0answers
28 views

How to create a covariate × time interaction term in Cox regression?

In Cox regression, it is sometimes inevitable that the strength of a predictor will vary across time (Singer & Willett). This violates the proportionality assumption, but can be incorporated in ...
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1answer
66 views

Good resources on Aalen additive models (survival)

I'm trying to do some modelling of time to event data and for various reasons, the Aalen additive model seems promising. I'm using the aareg function in the ...
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55 views

Predict probability of failure in R using survreg

I am fitting a weibull model as follows: s <- Surv(DFBR[,"Time"],DFBR[,"Censor"]) wei <- survreg(s~ Group+ UsefulLife, data = DFBR, dist="weibull") How ...
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27 views

Survival Analysis and Predictor Variables

Suppose that we are modeling the log-hazard of death using age, gender, bmi, and weight. BMI and weight are correlated. Would it make sense to drop one of these variables from out analysis?
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26 views

Link function for log-logistic shared gamma frailty model

I've been asked to replicate a study that models an accelerated failure time survival model with a log-logistic distribution and gamma distributed frailty (a 'log-logistic shared gamma frailty model') ...
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11 views

Coefficients and Categorical Variables

Suppose that a categorical variable $X$ can take three values: $0$,$1$ or $2$. If we run a Cox proportional hazards model and get an estimate of $\beta_1$, how would we interpret this? So we get: ...
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11 views

Bias in predicting survival with time varying covariates

I'm trying to predict survival probabilities with time-varying covariates. My dataset constitutes a variety of subjects who enter the study at different dates and receive multiple follow-ups. For each ...
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21 views

Cox regression with interaction giving NA values, how to interpret? + Choosing covariates based on p-values

I am working with a dataset with 12 covariates(categorical). The covariates have different Levels, some are from 0-5, and one has as much as 0-11 categories. I started with a univariate analysis to ...
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21 views

Question on late entry in Survial Analysis

In the example mentioned in the this doc for Survival Analysis on how to define time intervals, it says that the logic for creating the time variables is that, if a subject has no events, there is a ...
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22 views

Assessing accuracy of randomForestSRC on a survival data

In the randomForestSRC in R, we have the example ...
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20 views

Predicting a Certain Type of failure and deciding the input time series

I am trying to predict the time to certain type of failure given the following data on Certain Factory Equipments. The data I have are readings collected every day for sensor installed on those ...
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1answer
37 views

Cohort analysis for media site

I'm trying to find a reasonable way to measure retention of a site (news site). I'm trying to do cohort analysis: I've grouped all visits by year/week, and measured the percent of users that kept ...
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0answers
16 views

How to construct a design matrix for coxph with pspline term?

I am wondering how to reconstruct the design matrix for a coxph() model with a pspline() term. For example, if I fit the ...
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0answers
12 views

Relation between median follow-up and median survival?

When follow-up is assumed to be constant and variable, is there any relationship between median follow-up and median survival? I.e. should one be less or greater than the other?
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17 views

AFT model with frailty for right censored life time data

Let say I have a 'kidney catheter' data set. Data are about the recurrence times to infection, at the point of insertion of the catheter, for kidney patients using portable dialysis equipment. ...
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33 views

repeated measures survival analysis

I have various samples on which three survival time variates have been collected. How can I compare the difference of such variates taking into account within subject correlation (possibly in R)?
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1answer
59 views

The right way to report random effects in a Cox survival model

I have a data set (patients (15000) nested in hospitals (50)), with a number of covariates. I built a proportional hazards model in Stata, and entered site as a frailty term. I would like to report ...
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2answers
86 views

Interaction terms in Cox PH model

I am wondering if there is a way to interpret an interaction term from the coefficients rather than just looking at the survival curves? The factors involved are A, B, and C, which are all binary ...
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0answers
8 views

Tests behind comparison of a sample's survival to that of the general population

In the literature there are often reports of comparisons of a sample's survival to that of the general population. Life and mortality tables are cited however the tests and statistical procedures ...
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1answer
56 views

Compare Survival in Days using Mann-Whitney-U Test

I already read across the CrossValidated StackExchange, but didn't find an answer on the following problem. I have different groups of animals which have survival rates given in days since first ...
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1answer
81 views

Predicting new data using a Case-cohort Proportional Hazards Model

I am fitting a Case-Cohort Proportional Harzards (CCH) model using the Survival (version 2.37-4) package in R 2.15.3. Normally with a Cox Proportional Harzards (coxPH) model, I can use the survfit ...
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29 views

Variable effect in Weibull and Cox models

Is it possible to compare effect of variable on the survival time in the Cox model and in the Weibull regression model?