survival

  1. R

    Survival analysis at few dates: glms? logrank? cox ?

    Hello, In many documentation I have read that Kaplan-Meier curves followed by logrank test and/or cox models are the most recommended statistical methods to analyse Survival and test for different factors that may impact the Survival. However, I have also heard that these are suitable if I...
  2. P

    Should IRRs and HRs always be equal?

    I am running an analysis in a large population registry where individuals enter and leave the dataset at different time points. When i estimated the IRR between two distinct groups and a health outcome, and then a HR, I am finding a small difference (IRR 2.18, HR 2.01). Shouldn't they have...
  3. F

    IPTW survival analysis with crossed KM

    Hello, i am new here but i have the feeling, i will be around for some time. Off to my question now :) I am currently doing a survival analysis between two groups of patients that either received an event (surgery) or not. I want to find out, how this affects different survival endpoints. Now i...
  4. S

    a logarithm transform of a predictor fixed proportional hazards in Cox model - how can that be ??

    0 down vote favorite I have survival data to which I am fitting a Cox model with a continuous predictor. The cumulative martingale residual method (supremum test) of Lin, Wei and Ying...
  5. K

    How to do power analysis

    I want to do power analyses prior doing statistical tests on data to assess for the power it would yield. It mostly is survival data. I want to use Cox etc. What will you recommend, how to perform these?
  6. C

    Kaplan-Meier Estimate

    Let T_i is the survival time for individual i (i=1,2,\ldots, n) and C_i be the time to censoring. Let U_i=\min(T_i,C_i). And \hat S(U_i) is the Kaplan-Meier estimator for the censoring distribution. Suppose R_i and Z_i are two indicator functions. Also,p is a probability. Consider the following...
  7. D

    Correlated variables in Cox model - which one is best

    Hi there, I am building a Cox model. I have two variables that are different measures of the same thing and they are therefore correlated with each other. Both variables are strongly associated with survival. My understanding is that it is not ideal to place correlated variables in the same...
  8. B

    How to obtain an unbiased post-stratified estimator for survival probabilities?

    Suppose I have estimated the survival probabilities $\hat{S(t)}_1, \hat{S(t)}_2, \ldots, \hat{S(t)}_H$ from $H$ strata. Now I want to get an unbiased estimate of population survival probability $S(t)$ using these stratum-specific estimates. Then what should be the estimator? Should it be...
  9. C

    Cox's regression

    Hello, I have some experimental data for animals with tumours. Unfortunately, they were not followed individually during a time course, but evaluated as groups. As a result, I have 6 predictors only for animals that have survived for each time point. I would like to test which of these...
  10. L

    Kaplan Meier Curves With Repeat Events? Is it Possible?

    This may be a stupid question, but: can you construct Kaplan-Meier curves for repeat event data? Or should I limit each individual to occurrence of the first event? Thanks so much everyone! -Laura
  11. S

    Possible stats tests to use?

    Hi, After racking my brain not knowing what to do with my data I thought I'd give it a shot and post here, as I'm still unsure what I can do to test it. Movement count per 10 seconds and survival was measured in the same animals along entire lifespan at set time points, such that when...
  12. A

    Incorporating correlation between parameters using variation-covariance matrix

    Hi all, My colleagues and I are working on a project (i.e., health economics model) where we have fitted parametric curves (using Weibull, Exponential, Gompertz, Log-logistic, Log-normal, and Gamma distributions) to Kaplan-Meier data. In the project, we have estimated various survival curves...
  13. P

    Difficulty calculating probability of a complicated event

    Trying to calculate this statistical issue for work, not sure if I am over complicating or what - but certainly need some help in solving. For whoever can help, if it can be done on Excel, that would be extremely appreciated. I am looking at the clinical risk of a particular drug being taken...
  14. T

    Difference between SPSS and r standard errors in glm Probit analysis?

    Hello all, My name is Edwin R. Burgess, I am a Ph.D. candidate in biology at Northern Illinois University. My dissertation is being done on the effects of commonly used filth fly pesticides on parasitic wasp species used for biological control. Right now, I am doing binary mortality response...
  15. E

    Survival analysis - two different end of study times

    Hi I am analysing time to event data using Cox Regression (SPSS) as there are a number of covariates to be included. Previously, the end of the study was 2009. Recently, some participants who were recorded as not having had the event by 2009, were found to have had the event by the end...
  16. C

    Mean Residual Life

    Hi, I've been tasked with solving the mean residual life given the density function f(x) and the survival function S(x) I think mean residual life can be calculated by: mrl(x)=[∫(t-x)f(x)dt]/S(x)] or mrl(x)=∫S(t)dt/S(x) the problem is, f(x) contains the gamma function and I don't...
  17. O

    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...
  18. S

    Physics-style Repeated Measures of multiple predictor variables in survival analysis?

    I have inherited a longitudinal dataset where 5 different continuous independent variables were measured multiple times daily for 28 days in individual subjects. Measurement intervals were irregular, both within and between subjects. These independent variables have a relatively high variance...
  19. B

    Multiphase Survival Estimation - Data Modeling & Collinearity (Stata)

    Dear Forum Members and Statistics Ballers! I am currently trying to model a survival function for entrepreneurs, and would like to specifically test the impact of covariates during certain phases of the endeavor. Simply: Does a Covariate have a stronger or weaker effect during any of the...
  20. F

    kaplan-meier from a survival function

    hi, let assume I have a survival function, given as a solution from a continuous model. To be precise, the cumulative hazard is calculated, Ch(t), and then S(t) = exp(-Ch(t)). How would you simulate a Kaplan-Meier plot based on this? Here, the so called clinical trial simulation is performed...