In many articles (psycholinguistic), I see that linear mixed models used were centered and factor levels were coded (example , two factor levels were coded as -.5 and .5. In those research, there are usually random factors included intercept for subject and items.
Anybody to explain this and to recommend practical examples to be carried out under R?
Many thanks in advance
Rachid
https://web.stanford.edu/class/psych252/section/Mixed_models_tutorial.html
thank you
i already read this document but did not find any explanation...
Here is a paper explaining it in full ( Article The Effect of Different Forms of Centering in Hierarchical L...
).The Kreft and de Leeuw multilevel book also covers it in detail. In R this can mean using the scale function. In many cases it is worth thinking about how to transform variables to make interpretation clear (e.g., with interactions). Also centering can prevent some computation problems for some problems.
I unable to find this book for the moment.
Is there an ebook that could be find easily and in which I could find some practical examples with R, as for example situation with two fixed factors (two levels with each as example) and random factors (subject and items). My knowledge in mathematical and statistical sciences are very limited... thank you
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