Fig. 2From: Power and sample size analysis for longitudinal mixed models of health in populations exposed to environmental contaminants: a tutorialPower for time-by-group interaction, as a function of mean difference [(μ T1,A - μ T3,A) -(μ T1,C- μ T3,C)] and standard deviation of PFHxS. Data are back-transformed for interpretability. The standard deviation shown is 3.02 ng/mL. This mean difference is scaled by factors of 0.5, 1, 1.5, and 2 along the x-axis. The solid line shows how differences in the mean difference may affect power. Additionally, the two dashed lines show how the relationship between the mean difference and power changes when the standard deviation is smaller by half (1.51 ng/mL) or doubled in size (6.04 ng/mL)Back to article page