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. Author manuscript; available in PMC: 2010 Jan 4.
Published in final edited form as: J R Stat Soc Ser A Stat Soc. 2008 Jan 1;171(1):179–202. doi: 10.1111/j.1467-985X.2007.00511.x

Fig. 1.

Fig. 1

Sources of ecological bias: (a) Group intercepts correlated with covariate group means. (b) Group slopes correlated with covariate group means.