Search results

  1. hlsmith

    Trend analysis

    When was the protocol implemented? if it was within the about timeline you should add a vertical reference line, to distinguish the control and intervention periods. Were there different variable to control for besides the passing of time that may influence the MRI readings/diagnosis that need...
  2. hlsmith

    Variance contribution testing

    So all variables are at the county level? What do you mean by "has a large variance"? It may be beneficial to look to the oncology or epidemiology literature to see if similar study control for a covariance structure between tangential counties.
  3. hlsmith

    Survival Analysis

    K-M curves are typically like the initial bivariate analyses before logistic regression. As noted you would use Proportional Hazard Regression (e.g., Cox). The interpretation of the model is comparable to that of logistic regression, effect of exposure while holding covariates constant. Just...
  4. hlsmith

    Confidence interval for Difference in Differences?

    Yes, I refer to this article about once a year or so to remember some of the intricacies.
  5. hlsmith

    To assess meaningfulness between an independent variable and a dependent one, is just the p value alone adequate and/or the correlation?

    Just keep sampling variability in mind which can be seen when looking at 95% confidence intervals. Estimates from smaller samples have the potential to vary given variability in the selected sample. You become more certain of the estimate with larger samples.
  6. hlsmith

    To assess meaningfulness between an independent variable and a dependent one, is just the p value alone adequate and/or the correlation?

    I like the above posts. I will add as well that a statistically significant result (e.g., slope) can help rule out chance, though if its effect is small an investigator may want to remember that it may not take that large of an effect of an omitted variable to account for the effect. Such as an...
  7. hlsmith

    Confidence interval for Difference in Differences?

    I see you used SAS code, so check out this reference. You may be able to adjust the code to output CIs. Also, I am using this reference in case you did not randomize group assignments, so you have a risk of non-ignorability of treatment assignment - AKA confounding based on baseline covariate...
  8. hlsmith

    Hola to all!

    Welcome aboard. We look forward to your questions and contributions. :)
  9. hlsmith

    Trend analysis

    What study, did you actually intervene some how or what would have driven clinicians to order MRIs faster? You may want to rerun the model without the outlier just to make sure the outlier isn't pulling the line up, but likely you won't see a difference.
  10. hlsmith

    Should i use McNemar's for a matched-pair study?

    What is the standard deviation of these values, the issue would be that say + 2(std) may be something like 30, which would not be possible if the top value has to be contained within 100. Are the scores a percentage, if so you may want to investigate beta regression.
  11. hlsmith

    Trend analysis

    Yes, but I imagine you had more than 30ish MRIs performed over 14 year period? Are these the raw delay values for each MRI conducted? Also, you would want to confirm the high plot was really an outlier and not a calculation or data recording error. Next you would look to plot a line to these...
  12. hlsmith

    To assess meaningfulness between an independent variable and a dependent one, is just the p value alone adequate and/or the correlation?

    Are you using linear regression? If so, look at magnitude and direction of slope along with 95% confidence interval.
  13. hlsmith

    Jupyter notebook

    When I installed a jupyter notebook on my computer via anaconda, it auto-created a bunch of folders in it. Consisting of Music, photos, desktop, etc. Not sure what's up with that. Also, it tells me I can't delete some of the folders since they aren't empty, but they appear to be empty. Anybody...
  14. hlsmith

    Should i use McNemar's for a matched-pair study?

    What are the average scores? If the aren't around 50 or have quite a bit of dispersion, linear regression approaches can have problems. This is due to value being contained within 0 and 100.
  15. hlsmith

    Should i use McNemar's for a matched-pair study?

    Does each patient have a single match?
  16. hlsmith

    How can I control the format of the PCA analysis output in R?

    Why would it look the same for two different datasets? That doesn't make sense.
  17. hlsmith

    Bias correction

    You get prediction and have observed data, so you have residual or error data. Unless there is a pattern in the errors I don't know what you correct for, you just have bad fit. If you have a pattern you can try to transform data or tweak the model!
  18. hlsmith

    Linear Probability Model

    Referring to the logistic regression assumption of linearity in the logit, which isn't a concern when predictor is categorical.
  19. hlsmith

    Proportionate vs absolute count for analysis

    Your description is very vague. What procedure are you trying to use? Are you trying to use a Chi-sq test? Also, what program are you using? Also, I can't follow what you are looking at, how does 20 species translate to 15.5%; also if you don't use count based values, how does the program know...
  20. hlsmith

    Linear Probability Model

    I didn't exactly follow your quote, but is their lack of concern with a binary variable being you the slope between the two values is just a straight line. The same lack of concern in regards to the linearity of the logit for binary predictor versus a continuous predictor.