Fig. 1.

Amyloid (Aβ) group profiles and the smallest detectable effect, δ, based on Australian Imaging, Biomarkers and Lifestyle (AIBL) study of aging [10] with mixed-effect model assuming 80% power, 5% two-sided α, 3-year trial, and n = 500 per group. The assumed attrition for the active group is shown along the bottom of the figure (row marked by green square). The assumed attrition for the placebo group was 5% (n = 25 participants) less at each visit. This amounts to an assumed overall attrition rate of 30% over 3 years (i.e., 1 − (337 + 337 + 25)/1000 = 30%). The other rows of numbers along the bottom are the observation counts for the indicated group over time.

(Reproduced from Figure 1 of [1].)