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  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...
  16. Q

    Cox Regression Assumption

    Hi all, My Cox regression model doesn't validate the proportional hazards hypothesis. I think the other two assumptions are easy to verify. I used the 'strata' function in my model [ strata(hospital) ], but the proportional hazards assumption is still not validated. How can I do to validate...
  17. Q

    Help on an Old Script...

    It may be that a function in R no longer exists from one period to another. I advise you to search for the function mlogit.data(), see if the package and function still exist in R, and all the parameters of the function. https://www.rdocumentation.org/packages/mlogit/versions/1.1-1/topics/mlogit
  18. Q

    How to find the best regression model

    These are sub-samples at different points in time, I need to assess for each sample whether the variables that are significant are the same regardless of sample and time or not. It may be that the models of the two different sub-samples have different variables. But what criterion should be used...
  19. Q

    How to find the best regression model

    Yes, I have some models with differents variables and the same data. I used AIC to find the best model. But now I have some models with differents variables and an other data. I used AIC too, to find the best model with this data. But how compare and find the best data between the model where...
  20. Q

    How to find the best regression model

    Hello, @Karabiner , @fed2 thanks guys ! And if I have two regression models, with same variables but different data ( a sample and a sub-sample of this sample ), can we compare them with AIC?