2 Matching Annotations
 May 2019

stats.stackexchange.com stats.stackexchange.com

Multiple comparisons: It is not good practice to test for significant differences among pairs of group means unless the ANOVA suggests some such differences exist. Nevertheless, I admit it is tempting to take another look at the comparison of G1 with G3 (ignoring the existence of G2 and perhaps assuming normality), but then you should use a Welch t test to account for the differences in sample variances, and you should not make claims about the result unless the Pvalue is as low as .01 or .02. Looking at that difference more carefully might prompt a subsequent experiment.
Test for significance among pairs when the overall f test is not significant.

 Jan 2016

tachesdesens.blogspot.com tachesdesens.blogspot.com

Nothing would have changed
This is always a retrospective view. Always worry about the post hoc view that this represents. Perhaps the change was inevitable given the set of initial conditions the classroom represented at this point in time. Perhaps we need the hard rock problem that the status quo ante bellum represents. Perhaps it is just one narrative of many that are equal to more compelling.
