Contact Timing and Survey Completion Following Repeated Outreach: A Retrospective Attempt-Level Analysis

Repeated outreach is often necessary in longitudinal research, yet observational analyses of contact timing can be misleading when they reduce a participant’s history to the final recorded contact. We reconstructed 21,402 contact attempts involving 4440 former university students invited to complete a health survey between 2020 and 2025. Contact attempts were ordered relative to exact survey-completion timestamps. We examined completion within 1, 2, 7, and 14 days of eligible contact attempts using logistic models with participant-clustered robust standard errors. Models adjusted for attempt sequence, calendar year, and the interval since the preceding contact attempt; time-of-day models also adjusted for weekday. Recorded time of day was not associated with completion in any response window (global p values = 0.210–0.770). Weekday tests were statistically significant across windows, but Monday through Friday were generally similar. In the primary 7-day model, Saturday contact attempts were positively associated with completion (OR = 1.50, 95% CI [1.03, 2.19]) and Sunday contact attempts negatively associated with completion (OR = 0.19, 95% CI [0.09, 0.40]), relative to Tuesday. These opposing weekend estimates arose from relatively small, selectively scheduled samples and should not be interpreted causally. No consistently optimal weekday or hour emerged. These findings illustrate why contact sequence, response latency, and repeated observations should be incorporated before observational outreach records are translated into scheduling recommendations.