Abstract
Appropriately centering Level 1 predictors is vital to the interpretation of intercept and slope parameters in multilevel models (MLMs). The issue of centering has been discussed in the literature, but it is still widely misunderstood. The purpose of this article is to provide a detailed overview of grand mean centering and group mean centering in the context of 2-level MLMs. The authors begin with a basic overview of centering and explore the differences between grand and group mean centering in the context of some prototypical research questions. Empirical analyses of artificial data sets are used to illustrate key points throughout. The article provides a number of practical recommendations designed to facilitate centering decisions in MLM applications.
Original language | English (US) |
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Pages (from-to) | 121-138 |
Number of pages | 18 |
Journal | Psychological Methods |
Volume | 12 |
Issue number | 2 |
DOIs | |
State | Published - Jun 1 2007 |
Keywords
- centering
- grand mean centering
- group mean centering
- hierarchical linear models
- multilevel models
ASJC Scopus subject areas
- Psychology (miscellaneous)