Recent content by hlsmith

  1. hlsmith

    Strange results of logistic regression

    Well, when dealing with interactions terms it is standard practice to ignore base terms in the model since they are conditional on each other and don't have an independent interpretation. Thus, you shouldn't care about the base terms. We can see the interaction term did not change, which is what...
  2. hlsmith

    Whats the quickest way to learn stata for my uni course?

    Do you already know any programming languages, if so once you know one, new ones aren't too hard. This day and age everything is on youtube or Google searchable! So don't worry too much.
  3. hlsmith

    What test should I do?

    I saw this, these weird tricks always amuse me.
  4. hlsmith

    Regression analysis - difference as dependent variable

    How big is your sample size? Can you standardize differences and just run a simple regression with age groups dummy coded? Why not use actual age differences instead of categories? Peace.
  5. hlsmith

    pre-post outcome score for intervention and control groups

    We need much more information, such as was the intervention randomized, what are the sample sizes, is the outcome continuous (how is it distributed) or categorical, etc..... This is like me asking you what type of car to buy. So what type of car should I buy :)
  6. hlsmith

    What test should I do?

    Agree with @staassis - is there any more info. We have no idea of the distributions and they don't say assume a guassian distribution or any hints. @GretaGarbo - do you have any intel to guide them. You seem to know things in this area. If there were a little more info you could simulate two...
  7. hlsmith

    Include supplementary individuals PCA with PROC PRINCOMP

    I don't know how @ondansetron extrapolated that from your post. Why don't you just create a deterministic data split conditional on pulling out certain rows or more likely in SAS, OBS. You would sort data based criteria to create repeatability, then add a count variable, then perform a data...
  8. hlsmith

    Whats the quickest way to learn stata for my uni course?

    Start trying to use it right now. What is the course content you will be covering?
  9. hlsmith

    Strange results of logistic regression

    Results should be comparable. Post code and output for your last two listed models and we will help unpack the results. This is the easiest way for us to see what you are doing and writing about. Thanks!
  10. hlsmith

    developing and assessing a prediction Cox model using lasso

    Not really, but if you have terms you want to control for in the model regardless - you should do it. I have not done that, but I would image that some may have their coefficient shrunk to 0, so I am not sure how you treat that, since if scoring data you would have a zero product (e.g., age =...
  11. hlsmith

    Confidence levels

    I get 95.44% Confidence Interval. I can provide more details if needed, see if you can use this to get their interval values.
  12. hlsmith

    Confidence levels

    So you have everything but the standard normal value, right? Well if you are getting close to say 1.96, it's probably just a rounding error, even if you have the dataset, the mean, std, or zvalue - they can all be rounded. Post all of the parts and we will tell you what we get.
  13. hlsmith

    developing and assessing a prediction Cox model using lasso

    What is the purpose? Many would say that model 1: y-hat = X1 + X2 + X3 is not the comparable to model 2: y-hat = X1 + X2. You can test if adding X3 is beneficial, but they are two different models so you have X1 controlling for X2 and X3, as well as X1 controlling for X2 in the latter model...
  14. hlsmith

    Confidence levels

    What are "confidence levels"? Can you provide a lengthier description of the problem and its context?
  15. hlsmith

    developing and assessing a prediction Cox model using lasso

    Hmm, unfortunately I don't have the faculties to read that large CV thread right now. For clarity, you have an overall sample size of 200 patients? What is the prevalence for survival in the overall set? With that many candidate predictors, I wonder if the genome (GWAS) community may have a...