Volume 8, Number 1—January 2002
Research
Participant Blinding and Gastrointestinal Illness in a Randomized, Controlled Trial of an In-Home Drinking Water Intervention
John M. Colford*†
, Judy R. Rees*†, Timothy J. Wade*†, Asheena Khalakdina*†, Joan F. Hilton‡, Isaac J. Ergas*, Susan Burns*, Anne Benker*, Catherine Ma, Cliff Bowen, Daniel C. Mills, Duc J. Vugia, Dennis D. Juranek¶, and Deborah A. Levy¶
, Judy R. Rees*†, Timothy J. Wade*†, Asheena Khalakdina*†, Joan F. Hilton‡, Isaac J. Ergas*, Susan Burns*, Anne Benker*, Catherine Ma, Cliff Bowen, Daniel C. Mills, Duc J. Vugia, Dennis D. Juranek¶, and Deborah A. Levy¶Table 2
Final (Week 16) Device Blinding Questionnaire, Pilot Water Evaluation Trial
| Index respondents only | |||
|---|---|---|---|
| Guess | Sham device group (%) | Active device group (%) | Total (%) |
| Sham | 5 (16.1) | 5 (15.2) | 10 (15.6) |
| Active | 13 (41.9) | 19 (57.6) | 32 (50.0) |
| Don’t know | 13 (41.9) | 9 (27.3) | 22 (34.4) |
| Total | 31 (100.0) | 33 (100.0) | 64 (100.0) |
*Does not include 21 participants from the sham device group and 13 participants from the active device group who did not complete the final blinding questionnaire.
+Blinding index for all participants (adjusted for intrahousehold correlation, ρ=0.60)=0.64 (95% confidence interval [CI] 0.51–0.78). Blinding index for index respondents alone = 0.65 (95% CI 0.53–0.76).
