non-normality

  1. U

    When are non-parametric tests more desireable than a scale transformation when working on non-normal data?

    When, during an exploratory analysis, should one go for a robust test instead of a logaritmic/Box-Cox transformation of a variable if the Shapiro-Wilk test to verify the normality of the distribution of said variable is significant? Also, if I transform a variable with a logaritmic or a box-cox...
  2. 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...
  3. M

    [R] How to get normal/ rankit scores from non-normal data with ties.

    Hello, I would like to see whether pathogen levels influenced certain bumblebee colony development parameters such as the number of queen pupae produced. Due to non-normality of the data I would like to do a rankit transformation of the data as suggested by [Bishara & Hittner (2012)][1]...
  4. B

    How to perform reverse score transformations? (non-normal data)

    Hello, Sadly, my data are significantly non-normal, negatively and not positively skewed, so that leaves me, according to some statisticians, with only 1 available option (reverse scoring transformations; log, square root and reciprocal transformations I've heard that work wonders on positively...