raphaelvallat/pingouin: v0.3.2

Hotfix release to fix a critical issue with pingouin.pairwise_ttests() (see below). We strongly recommend that you update to the newest version of Pingouin and double-check your previous results if you've ever used the pairwise T-tests with more than one factor (e.g. mixed, factorial or 2-way repeated measures design).

Bugfixes

• MAJOR: Fixed a bug in pingouin.pairwise_ttests() when using mixed or two-way repeated measures design. Specifically, the T-tests were performed without averaging over repeated measurements first (i.e. without calculating the marginal means). Note that for mixed design, this only impacts the between-subject T-test(s). Practically speaking, this led to higher degrees of freedom (because they were conflated with the number of repeated measurements) and ultimately incorrect T and p-values because the assumption of independence was violated. Pingouin now averages over repeated measurements in mixed and two-way repeated measures design, which is the same behavior as JASP or JAMOVI. As a consequence, and when the data has only two groups, the between-subject p-value of the pairwise T-test should be (almost) equal to the p-value of the same factor in the pingouin.mixed_anova() function. The old behavior of Pingouin can still be obtained using the marginal=False argument.

• Minor: Added a check in pingouin.mixed_anova() to ensure that the subject variable has a unique set of values for each between-subject group defined in the between variable. For instance, the subject IDs for group1 are [1, 2, 3, 4, 5] and for group2 [6, 7, 8, 9, 10]. The function will throw an error if there are one or more overlapping subject IDs between groups (e.g. the subject IDs for group1 AND group2 are both [1, 2, 3, 4, 5]).

• Minor: Fixed a bug which caused the pingouin.plot_rm_corr() and pingouin.ancova() (with >1 covariates) to throw an error if any of the input variables started with a number (because of statsmodels / Patsy formula formatting).

Enhancements

• Upon loading, Pingouin will now use the outdated package to check and warn the user if a newer stable version is available.

• Globally removed the export_filename parameter, which allowed to export the output table to a .csv file. This helps simplify the API and testing. As an alternative, one can simply use pandas.to_csv() to export the output dataframe generated by Pingouin.

• Added the correction argument to pingouin.pairwise_ttests() to enable or disable Welch's correction for independent T-tests.