Timeline for Repeated measures ANCOVA interpretation – significant covariate/test day interaction
Current License: CC BY-SA 4.0
10 events
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| Aug 12, 2022 at 18:45 | comment | added | EdM |
@DruidRaves-V yes, I was looking at the wrong columns and have deleted my comments. Violating ANCOVA assumptions doesn't make lapses results uninterpretable, it just means you can't interpret the model without specifying a value for the covariate used for adjustment, lapses_t01. If you specify a value for that, you can interpret the model. Also, as you don't show the coefficient values themselves, you might be in a situation with a statistically significant (barely, p = 0.042) interaction that isn't practically important.
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| Aug 12, 2022 at 3:03 | comment | added | Druid Raves - V | Let us continue this discussion in chat. | |
| Aug 12, 2022 at 2:58 | comment | added | Druid Raves - V | I think you are looking at the wrong value. The p-value is the third from the right, and the star indicates that only lapses_t01 and lapses_t01:Testday are significant. The values in the outer right column are generalised eta squared, not p-values. | |
| Aug 11, 2022 at 21:44 | vote | accept | Druid Raves - V | ||
| Aug 11, 2022 at 21:40 | comment | added | Druid Raves - V | Okay... given the available function/output, would you agree with the following though? "Mixed RM ANCOVA revealed a significant interaction effect of the covariate, number of lapses at baseline, and Testday (F2,76 = 3.31, p = 0.04, η2G = 0.03), indicating interdependence of these variables. As this violates the assumptions of ANCOVA, the results for this variable (i.e. number of attention lapses) are not reliable and should not be interpreted." ? Or is this incorrect? | |
| Aug 11, 2022 at 16:34 | comment | added | EdM |
@DruidRaves-V the coefficient estimates and their covariance matrix, which should be provided by the modeling function, can let you interpret associations of lapses with the predictors. You just need to specify values of all three predictors--lapses_t01, Testday and Condition--as their interactions mean that the association of each with outcome depends on the levels of the others. Their individual coefficients are for situations when the others are at 0 or reference levels. The Type III ANOVA summary used by get_anova_table() was probably inappropriate for your data.
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| Aug 11, 2022 at 10:18 | comment | added | Druid Raves - V |
Thank you for your explanations! Unfortunately, I am not in the position to adjust the analysis at this point. From what I understand based on your explanations, the ANCOVA results for lapses cannot be directly interpreted, is that correct?
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| Aug 7, 2022 at 15:46 | comment | added | dipetkov |
It's by the author of survminer which speaks for itself.
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| Aug 7, 2022 at 15:45 | comment | added | dipetkov |
rstatix is a supposedly "simple" way to do statistics within the "tidyverse". In practice this means rstatix calls the well-known statistics packages (base stats, emmeans, car) in a obscure way so that it's never clear what model was actually fitted. For example, according to the anova_test docs: "type = 2 is the default because this will yield identical ANOVA results as type = 1 when data are balanced but type = 2 will additionally yield various assumption tests where appropriate. When the data are unbalanced the type = 3 is used by popular commercial softwares including SPSS."
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| Aug 5, 2022 at 17:14 | history | answered | EdM | CC BY-SA 4.0 |