# survival analysis

1. ### How to do survival analysis in SAS with interval censoring and random effects

Hi, I am interested in using survival analysis methods on seed germination data. I have just started reading Allison's Survival analysis in SAS. Accelerated failure time analysis (using PROC LIFEREG) and Cox proportional hazards models using PROC PHREG seem promising, but I have a feeling...
2. ### Relationship between sample mean and sample survival probability

I am not sure if this question is very naive, but I was wondering if there is a relationship between sample mean and sample survival probability. For an exponential distribution with mean mu, S(t)=1-exp(-t/mu}) Now if I generate data from an exponential distribution, can the sample mean...
3. ### Simulation of remission and after remission times under specific conditions

This is basically a data generation problem. Say, t is an exponential lifetime with mean two years. tr is the remission time and ts is the after remission time. So, t=tr+ts. I need to simulate these quantities for 100 patients. Now in real life, usually when tr is smaller, that is when the...
4. ### Validation of survival data / models

Hello, I'm currently analysing a couple of survival data with parametric survival analysis (AFT and PH) in STATA 12. I'm investigating different parameters and different distribution function. To chose the best available model I'm using an information criterion such as AIC or BIC. So far so...
5. ### Data management snapspan life table survival analysis

Hi :wave: I'm having trouble with the data management necessary to set the database so that I can run a Lifetable to do some descriptive analysis. I tried a simple snapspan synthax: snapspan id year x1-x15, gen (year0) but i'm getting an error message (which said "not sorted", even if I...
6. ### [Life table] Explaining an anomalous result

I am running a life table of marriage survival times using national data, the National Survey of Family Growth (N = ~8,500). Time-to-event is the time elapsed, in months, between when a marriage is formed and when it ends. Marriages intact at the time of data collection are censored; marriages...
7. ### Survival Analysis SPSS: Repeated Events

Dear TalkStats Forum, Does anyone have experience using SPSS for survival analysis when there are repeated events? the good news is, I'm still in the "design" stage of the research, so it's not too late to dramatically change the approach. Here's the basic setup: We have 50...
8. ### Discrepencies between SPSS and SAS

Does anyone know why there are differences in results when performing Kaplan Meier survival analysis tests in SPSS and SAS. The values do not match exactly and the bigger the sample population, the wider this difference becomes. Does anyone know what the difference in algorithms might be?
9. ### [EHA - SURVIVAL Packages] Fixed Effects for parametric models

Hi All, I am working on Event History Analysis using a recurrent events dataset. Does anybody know how I can include fixed-effects to control for unobserved heterogeneity in parametric models (such as: Weibull, Log-logistic, Log-normal, Gompertz)? Are there any functions that...
10. ### Cox Proportional Hazards Regression

Hi, I am hoping someone can help me with which model (frailty, strata or cluster) I should use for my data. I have paired data so I need to take that into account when modelling the Cox PH Regression and am unsure which model will give me a more accurate result. My study was looking at the...
11. ### Survival analysis with long term survivors

Hi all, Hope someone can offer me some advice here. I need some help getting off the ground with running a survival analysis with long term survivors (i.e. an unknown portion of individuals who may never experience the event being measured). I've been reading around the topic and...
12. ### Significance testing with survival analysis (actuarial method)

Hi, I'm teaching myself survival analysis with free resources on the web. I'm quite confident that I'm correct, but I just want to clarify that I have interpreted everything correctly! I am comparing the survival of a control and test group. I want to determine whether there is a...
13. ### [SPSS] Kaplan Meier not showing censored data

Hi, I'm trying to compare two Kaplan Meier survival curves in SPSS. It's about the overall survival between two groups. Now I've entered the months (as time), the status (0=censored, 1=deceased) and I put my variable 'group' into the factor box. But then, when I analyze, it doesn't show...
14. ### log-rank (or other) test for difference between survival curves

Hi, all. I have co-opted some R code that estimates parameters for a Gompertz-Makeham mortality model. The data to which the model is fit is interval censored, with counts of individuals in each age-range category. For example: naga <-...
15. ### 1 predictor, 2 different values for baseline statistic & change statistic?

Hi, I am conducting a Cox Regression for my first time. I created a simple model with only 1 predictor (categorical), one dependent variable (continuous survival time), and 1 event that defines whether the hazard criterion was met (dichotomous). Since there is only one step in this model, I...
16. ### proc PHREG all of my coefficients are zero?

Hi All, I am using proc PHREG to run a survival analysis and although I'm not getting any error messages, I'm pretty sure something is going wrong, because all of my chi-squared values and parameter estimates are coming out at exactly zero, no matter what model I run. Has anyone ever seen this...
17. ### What Test to Use? Survival...

Hi, I have 4 groups which each have a time to an event in months. I want to figure out if there is any significance between all 4 groups in the time it took for the event to happen. Is survival analysis the right test to use in this case? ex. Group 1 45 (months) Group 1 76 Group...
18. ### Independence of Observations in Survival Analysis

Hi. I have been trying to find some information on why concerns about dependence between observations in survival analysis is often not applicable even though generally data sets include multiple observations for a single individual. Is this something that is overlooked and not so much mentioned...
19. ### Confidence intervals for survival estimates with combinations of risk factors

Dear all, I have time-to-event data for patients with epilepsy. We have produced a parsimonious multivariable model for this event and therefore can obtain the probability of the event at each recorded time point. In addition to this, we can work out the survival estimate at a time point...
20. ### Using Age as Time Scale

I am generally a SAS user, I had a general question concerning how to fit survival models using age as the time scale within R. Would this fit be appropriate and also control for the left-truncated nature of the data? I know in SAS you need to specify a specific option. I was just...