Schematic of the Graeco Latin Square Design.

Interviewer/Fieldworker 1–5 (F1–F5).Interviewee 1–5 (S1–S5).Method 1 (M1): face-to-face interview & MRC standard paper-based data capturing and processing.Method 2 (M2): face-to-face interview & EDC using a netbook.Method 3 (M3): face-to-face interview & EDC using a tablet-PC.Method 4 (M4): face-to-face interview & EDC using a PDA.Method 5 (M5): telephone interview & EDC using a laptop.Order (O1–O5): Each interviewer/field worker interviewed 5 interviewees/volunteers per day. O1–O5 indicate the order in which the interviews were conducted (O1: 1st interview at a particular day, O2: 2nd interview, O3: 3rd interview, etc.).