Timeline for Rank deficiency in polynomial trend analysis
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
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| Sep 29, 2014 at 15:15 | comment | added | bunsenbaer | Excuse me for responding so late. In which (statistical) sense are interactions with blocking factors problematic? In my case, it is a reasonable assumption that persons scoring high on the trait I am interested in might "get bored/ lose motivation" faster than persons scoring only very weakly on that trait, hence showing a different profile of performance as the task proceeds. | |
| Sep 17, 2014 at 13:25 | comment | added | Russ Lenth | You get the warning because you are averaging over the levels of a factor that interacts with the one in question. You should look at (e.g., plot) the LS means for the combinations of those factors, and make sure that makes sense. Actually, I am a bit concerned about what you're doing with 'block'. Is it really a blocking factor? Usually, blocking factors are nuisance variables that we are not interested in - and usually, interactions with blocking factors are somewhat problematic. | |
| Sep 17, 2014 at 10:20 | comment | added | bunsenbaer | Thanks, rvl, for the comment. I did not know the function lsmeans() before and it seems nice for factors the effects of which do not depend on other factors. However, I'm additionally interested in interactions of "block" with personality traits, and for these analyses, lsmeans() gives me a warning that contrast estimates might be unreliable. However, I was aware before that specifying a null contrast was the same as using a factor with four equal factor levels and that it cannot predict anything. Alas, I remain confused about the term "rank deficiency". Perhaps, it only means the above said? | |
| Sep 16, 2014 at 13:35 | history | answered | Russ Lenth | CC BY-SA 3.0 |