Fig. 2From: Use of research electronic data capture (REDCap) in a COVID-19 randomized controlled trial: a practical exampleTime and number of study invitation emails sent with REDCap Survey Distribution Tools. Panel A. Cumulative number of responses to study invitation emails. Panel B. Number of responses to study invitation emails. * We resent the first study invitation to a portion of our initial sample because a subject line was omitted from the original emailBack to article page