Hello,
My initial thought was to compare the means by ANOVA combined with Tukey HSD post-hoc test. To verify the results i wanted to use Box-Whisker plot if several tools match with each other with an given specification limtit. It turned out, the residuals of each group (n=24; tools=10) are non normal distributed. I have read in the literature that for one-way anova the normal distribution for the residuals of a sample does not necessarly have to be fulfilled, if other assumptions (indenpendency, homogenity of variances) are not violated. Tests that variances are equal are passed by all provided tests in JMP. This was expected as same items were measured at different but same tools.
Link: https://www.researchgate.net/publication/232449663_Is_It_Really_Robust
Graphical anaylsis show that there is a (Mean/Median) shift between the groups, while the data points show evidence of symetrie.
I would actually like to stick to the paramteric test approach and not use non-parametric tests because it is easier to understand third parties.
My alternative would look as the following:
- Nonparametric Comparisons For Each Pair Using Wilcoxon Method
I already concudted the alternative. Using this approach does not really fit my graphical analysis, instead it tells me that most pairs a significant different.
Additional I already tried to tranform my data to log values, but this does not change anything as the groups itself show evidence of within 3 data clusters.
Thanky you for your feedback
Martin
