Search results

  1. O

    Normality: DV itself or residuals?

    I always thought that we should be testing the assumption of normality by looking at the distribution of the DV in our design (by each level of the IV). But I keep seeing people talking about the residuals of the DV. For example, in ANOVA (and I suppose by extension the t-test and regression)...
  2. O

    when does multiple comparisons become a consideration?

    Typically in research you collect data to test a specific a priori hypothesis. But nowadays many people generate hypotheses and then access appropriate datasets in online databases that have already been sampled and stored for general use. Is it valid to keep generating & testing new hypotheses...
  3. O

    Appropriate use of z-scores

    I was thinking about z-scores and I'm curious about their usage when data are skewed/non-normal. I often see zscores being used to identify outliers, e.g. with z>1.96, 2.58, etc. HOWEVER: the z-score calculation of z = (x - mean(x)) / stdev(x) is dependent on the mean, and the mean is not an...