Heterogeneity of Variance in Experimental Studies: A Challenge to Conventional Interpretations

@article{Bryk1988HeterogeneityOV,
  title={Heterogeneity of Variance in Experimental Studies: A Challenge to Conventional Interpretations},
  author={Anthony Bryk and Stephen Raudenbush},
  journal={Psychological Bulletin},
  year={1988},
  volume={104},
  pages={396-404}
}
The presence of heterogeneity of variance across groups indicates that the standard statistical model for treatment effects no longer applies. Specifically, the assumption that treatments add a constant to each subject's development fails. An alternative model is required to represent how treatment effects are distributed across individuals. We develop in this article a simple statistical model to demonstrate the link between heterogeneity of variance and random treatment effects. Next, we… 

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