covariate and its measurement [Devine and Smith, 1998]. Thus, if rG2 is the LD between a tag SNP and the causal SNP, and rE2 is the squared correlation coefficient between the true exposure and the measured exposure, we can expect an approximate sample size inflation of 1/rG2rE2. For example, if rG2=0.9andrE2=0.8, then the required sample size to detect a G×E interaction with a given power will be 39% higher than the required sample size if both G and E were measured without error.
