I am hoping someone can advise on the use of the Bonferroni correction. I am struggling to understand how and when to use it.
I have been part of a pilot study evaluating balance in older adults. We used several balance measures (sway area, sway velocity) with different parameters (eyes open/closed, solid/compliant surface), plus a timed functional test, measured on three occasions with the same subjects. I have performed separate repeated measures ANOVAs for each measure and parameter combination (7 in total) using SPSS, alpha set at .05. I understand the need to use the Bonferroni correction with the pairwise comparisons and that SPSS does this. However, I am unsure whether the correction needs to be applied across all the ANOVAs, namely whether I should set the corrected alpha level to 0.05/7 = 0.0071 when determining statistical significance for each individual ANOVA.
I understand there are debates around minimising Type I errors at the expense of Type II errors, but is the approach of using alpha of 0.0071 for each individual ANOVA fundamentally correct?
I wouldn't use any kind of adjustment (e.g. Bonferroni) across anovas on different dependent variables.
(Too brief of an answer, I know. Maybe someone else can weigh in with more explanation.)
Hello Matthew Holmes. I think that this pair of articles by Schulz & Grimes (2005) do a great job of discussing issues like the one you raise. Perhaps you will find them helpful.
https://pubmed.ncbi.nlm.nih.gov/15866314/
https://pubmed.ncbi.nlm.nih.gov/15885299/
HTH.
Hi Bruce Weaver , thank you, they are most helpful. They've told me what I needed to know.
No worries, Matthew Holmes. Despite being published nearly 20 years ago, those two articles remain among the best and most thoughtful discussions of multiplicity that I have seen (so far). ;-)
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