|  | Telephone interview | Self-administered questionnaire |  | ||
---|---|---|---|---|---|---|
Timing of information about second survey | Survey-mode sequence | PI M (SD) | PD M (SD) | PI M (SD) | PD M (SD) | N |
Delayed | Self-administered questionnaire first | 55.56 (19.3) | 31.20 (25.7) | 55.56 (19.8) | 34.53 (26.7) | 205 |
 | Telephone interview first | 52.32 (19.9) | 26.75 (25.4) | 52.68 (19.7) | 30.96 (24.7) | 194 |
 | Total | 53.99 (19.7) | 29.03 (25.7) | 54.16 (19.8) | 32.79 (25.7) | 399 |
At outset | Self-administered questionnaire first | 56.39 (17.8) | 31.06 (24.9) | 55.34 (20.4) | 34.55 (25.7) | 203 |
 | Telephone interview first | 56.00 (20.9) | 30.75 (26.2) | 55.68 (20.2) | 32.37 (24.3) | 190 |
 | Total | 56.20 (19.3) | 30.91 (25.5) | 55.50 (20.3) | 33.51 (25.0) | 393 |
Total | Self-administered questionnaire first | 55.97 (18.6) | 31.13 (25.3) | 55.45 (20.1) | 34.54 (26.2) | 408 |
 | Telephone interview first | 54.14 (20.5) | 28.71 (25.8) | 54.17 (20.0) | 31.65 (24.5) | 384 |
 | Total | 55.08 (19.5) | 29.96 (25.6) | 54.83 (20.0) | 33.15 (25.4) | 792 |