SCIENCE: Re-analysis on the statistical sampling biases of a mask promotion trial in Bangladesh: a statistical replication. “The purpose of randomized control trials is to establish a causal link between interventions and outcomes. However, causal implications are diminished in the presence of unblinding, ascertainment bias, and bias-susceptible endpoints. Unfortunately, in the Bangladesh mask trial we evidence of all of the above. . . . The mask intervention was highly effective at modifying behaviors (distancing, mask-wearing, symptom reporting). Nonetheless, the data is consistent with mask wearing having modest or no direct effect on COVID-related outcomes in this experimental setting.”