0todd0000/spm1dmatlab

Reference for comparing parametric vs. nonparametric results

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is there a reference I can look at where you suggest doing both tests and a comparison in the non-parametric scenario? Like a research paper or in the documention?

I think it would be acceptable to regard this this is just a general processing recipe:

  • Recipe 1: conduct both parametric and nonparametric testing, and compare the results.
  • Recipe 2: conduct normality test(s), then use these results to guide the choice of a parametric vs. nonparametric tests

Recipe 2 is more common, but the intent of both recipes is identical: avoid non-normality-induced errors. In my view, Recipe 1 is substantially better because it doubles as a sensitivity test, implicitly testing whether the final results are sensitive to analysis procedure particulars.

As a reference, I'd suggest Pataky et al. (2015), which implicitly suggests Recipe 1 in Figs.5-7, and especially in Fig.7. A free preprint of this article is available on ResearchGate

Pataky, T. C., Vanrenterghem, J., & Robinson, M. A. (2015). Zero-vs. one-dimensional, parametric vs. non-parametric, and confidence interval vs. hypothesis testing procedures in one-dimensional biomechanical trajectory analysis. Journal of biomechanics, 48(7), 1277-1285.