Recent content by ondansetron

  1. O

    p values, alpha, and errors

    It doesn't say anything about an error at any time, pre or post alpha, by itself. The statistical theory behind a p-value has nothing to do with error rates. Once you make a decision based on alpha and a p-value, you're correct or incorrect. In Frequentist statistics, it's irrelevant that you...
  2. O

    p values, alpha, and errors

    I figure that a true null encompasses all the assumptions, including model specification? If I test b1=0 for a slope in SLR, I’m assuming that b1 is the slope of a model where only x1 is in the true model. But yeah, it’s less obvious that your model needs to be correct, but really won’t be in...
  3. O

    p values, alpha, and errors

    Your definition of p value is incorrect and conflates alpha. The pvalue is the probability of obtaining a result at least as extreme as the observed one, assuming a true null hypothesis. This tells you, in simple terms, how much your observation disagrees with the null hypothesis. As you can see...
  4. O

    Need helping making something like a confidence Interval.

    If you used a confidence interval for "99% certainty" this likely is not a solved issue.
  5. O

    Statistical significance of observed incidence

    "Large" is a generally vague term but there exist rules of thumb for testing a proportion with z-test and chi-squared. In "large samples" z can be used to test for the true proportion, and will be equivalent to chi-squared. My point is this, you can use the chi-square or z-test to answer your...
  6. O

    Statistical significance of observed incidence

    What is the actual sample size? You can bootstrap a p-value or CI for the true proportion assuming a null hypothesis of p0= .316 with a two sided alternative. With a large sample (how large is large is always the real question) the z-distribution could be used for a proportion (or difference in...
  7. O

    Please help, which ANOVA should I use?

    Why are we ignoring Jun?
  8. O

    Please help, which ANOVA should I use?

    what about jun?
  9. O

    Critical F value for testing Full vs Reduced models.

    If you look at my post, I wanted the OP to come to this conclusion after seeing what results from calculating and F stat and a t-stat. I assumed this is homework so I took a harder stance :cool:
  10. O

    Critical F value for testing Full vs Reduced models.

    What are the pertinent formulae for computing F-statistics? What is the formula for testing individual coefficients with a T-test? Do you need one, both, or neither? Why?
  11. O

    Exponential smoothing models

    I agree with him on those grounds, absolutely, but that depends on the context. I think prediction is different from inferential modeling. In your case, you want practical results that equate to good predictions, right? If the toenail length of the firm's CEO allowed you to accurately predict...
  12. O

    Exponential smoothing models

    Some people in Economics believe that model assumptions shouldn't be based on how reasonable they are but how the model performs in practice. Maybe there isn't seasonality but the seasonality variable is proxying for another variable? If the end goal is predictive accuracy, then predictive...
  13. O

    Best statistical method for CFU/ml?

    Colony forming units per milliliter... if I were to take a guess... density of bacteria (or fungi) in (usually) a body fluid
  14. O

    Factor Analysis

    As far as I recall, SAS has different methods of PCA and FA since they are different methods with different goals. People often misuse one in place of the other, though, so be careful what you read on this internet!
  15. O

    Retrospective intention-to-treat analysis? what does it mean?

    Is it ITT in a retrospective study? ITT in a prospective study or RCT is a lot better because it mimics the real world situation where a physician may prescribe, but patients may end up as noncompliant in one way or another. I don't think ITT is bad. The BS to watch for is ""modified" ITT or...