Think Tank participants discussed the related issues of power and sample size. Because of small effect sizes, multiple testing corrections, and the need to model more parameters, studies of GxE interactions need to have large sample sizes. Table 2 provides a list of software that can be used for power calculations in GxE studies. Lack of power is an important limitation in many GxE studies, particularly GEWIS [Dempfle, et al. 2008; Mukherjee, et al. 2012]. The GWAS community was able to address sample size by performing meta-analysis, efficiently combining results across multiple studies [de Bakker, et al. 2008]. However, there are more challenges when considering meta-analysis of GxE (see Cornelius and Hu for discussion [Cornelis and Hu 2012]). Some of these issues overlap with issues in replication as discussed below.
