Duration of the interviews.

*Minimum and maximum duration of the interviews. **Comparison of the median duration of the interviews between the first and the last week of the study period for each device using the Wilcoxon signed-rank test. ***Mixed effect model fitting device, week, sequence and interaction terms for device/week, adjusting for random effects for the 25 combinations of fieldworker and device. P-values indicate if there was a significant reduction in duration of the interviews over the study period of three weeks. #Median duration for three interviews using the tablet PC. ##During the first week of the study 3 of 5 scheduled interviews for the EDC method using the tablet PC were conducted. The p-value of p = 0.109 for the non-parametric test might therefore not be a reliable estimate. Median duration for four interviews using the PDA.