If 50 subjects in the exercise group complete the 6- month measurement, then the study has 80% power to detect a difference of at least 2.5 points with a one- sample 2-sided t-test at the 0.05 level. That is, if cycling leads to a true mean increase in the ADAS-Cog of no more than 0.7 points, the study will have 80% power to detect a difference from the increase of 3.2 observed in placebo groups in AD drug RCTs. In our control group, if 25 complete the trial, then the expected half-width of the 95% confidence interval for the mean 6-month change in the control group is 2.4. Although there is little power to detect a difference between our controls and the pla- cebo groups in AD drug RCTs, our trial will provide a valuable estimate of the intervention’s Hawthorne effect.