Recent content by Q&A

  1. Q

    AIC models

    Thanks
  2. Q

    AIC models

    The prediction intervals are the confidence intervals, right?
  3. Q

    AIC models

    So if my p-value is significant, does that mean we should keep the full model? But if the full model contains a lot of variables, isn't there a way to remove some of them?
  4. Q

    AIC models

    Yes, that's right, I need a scale model. So in the case where we have an M1, M2 and M3 model. M1 has 6 variables and has the smallest AIC (5676) I would like to have a model with fewer variables. If I remove one variable from the model, the variable that has the highest p-value among all the...
  5. Q

    AIC models

    But I am looking for a reduced model because a model with several variables does not appeal to me in practice. What should I do?
  6. Q

    AIC models

    Hello, If I have a model with an aic of 8765 and another model reduced with two variables less with an aic of 8823. Can I accept the reduced model with the AIC of 8823? What is the difference between the two AICs that should not be exceeded? Thank you
  7. Q

    Generalized linear model: application conditions

    Hi, Yes I have adjusted my model, and used the VIF to remove the variables that had a too high VIF. But by doing a shapiro test on the residuals of my response variable which is a lifetime, I rejected the null hypothesis. So I don't know if having residuals from a normal distribution is one of...
  8. Q

    Generalized linear model: application conditions

    Hello all, I would like to know what the conditions are for the application of a GLM. Should we test if the response variable is normally distributed? (shapiro wilk) Is it a problem if my variables are correlated with each other but my observations are not? Thanks
  9. Q

    Testing log-linearity

    Ok thanks if it's horizontal it's validated. For exemple, if is it a curve that goes up and down or the opposite? How to interpret it? What to do? Should we reject the hypothesis?
  10. Q

    Testing log-linearity

    Hi all, I want to test the log-linearity assumption for a cox model. How to interpret the plot of martingale residuals? you need to have a horizontal plot, or a linear line, or ... In which case should the hypothesis be validated and in which case should it not be validated?
  11. Q

    Cox Regression Assumption

    I just said that on one case, I have a model with 239 deaths (censored observations) and 56 still in life.
  12. Q

    Cox Regression Assumption

    Hello again, I'm working with R, so for the non proportional hazard assumption, I used the coxzph function. But I have other questions in generally in Cox Model if you can help me. 1/ If my observed data is less than my censored data, is that a problem? (56 observations for my observed...
  13. Q

    Cox Regression Assumption

    what do you mean by "crossing"? I have to evalue variables that have impact in the death of these individuals , and it's the model that gives me variables responsible for the death.
  14. Q

    Cox Regression Assumption

    An in the strata function, we can use a temporal variable , time variable ?
  15. Q

    Cox Regression Assumption

    Yes, my Kaplan-Meier curves do cross each other. I've also seen articles saying that if you have this kind of problem, if the proportional hazards assumption is violated, you can add a stratification or an interaction term. You say interaction term, what exactly is that? How do you choose it...