Randomization, intent-to-treat, and power analysis
RECRUITMENT
Block randomization was used to assign participants to comparison groups. For each consecutive pair (block) of enrolled subjects, one member was assigned to the treatment arm, the other member to the placebo arm. The pseudo-random number generator in Microsoft Excel was used to generate random numbers to permit the treatment assignment within each block of subjects. Treatment assignment codes were generated and kept by the MVAHCS research pharmacist and stored on a secure VA server behind VA firewalls. All study participants and study personnel, except the research pharmacist, remained blinded to the assignments until the last subject had completed the final study visit.An intent-to-treat analysis was used for the outcome measures. All study participants had a calculable PCS and MCS at baseline. Missing values for the two participants who withdrew from the study were set to equal baseline scores (last-observation-carried-forward strategy).Power analysis was used to establish the GWIIRT recruitment goal. In a VA study of the effects of cognitive behavioral therapy and aerobic exercise on GWI, an intervention-related 7-point increase in the PCS with no change in the placebo arm was defined as clinically significant [