ABSTRACT
Questions about sample size tend to focus on two topics: what sample size is sufficient to apply a specific statistical method, and what sample size is needed to obtain a specific power. In multilevel analysis, these problems are made more difficult because there are sample size issues at more than one level, and because the model includes a fixed and a random part, and typically the fixed part can be estimated with more precision than the random part. This chapter reviews both the sample size and the power issues.
