However, we have shown elsewhere that, even when using Anonymized-Envelopes, survey respondents underreport their military sexual assault experiences by a factor of three [ 30].
If one participant returns more than one envelope-survey pair, all but the first is discarded.
Until the envelope and survey are separated, however, the survey is not truly anonymous.
The surveys for this group were sent to a postal address nominated by the participant and also included pre-paid envelopes for survey return.
In Japan, studies that receive public funds are not allowed to offer incentives or stamped reply envelopes to survey participants as participants may not respond, and such a practice is regarded as a waste of research expenses for a study supported by the national government.
Additionally, first-class stamps on reply paid envelopes, short surveys, personalised and studies endorsed by professional organisations were more effective.
In a randomized controlled trial we examined the effect of sending a prenotification postcard before the questionnaire and the placement of a short message on the survey envelope (teaser) on response rates to a mailed questionnaire about bulimia nervosa "mental health literacy".
Each such patient received a package containing an information letter, informed consent documents, a pre-stamped return envelope and the Survey of Sleep questionnaire (SOS).
Specific procedures included a stamped return envelope with the survey, a series of planned contacts with all intended recipients, the provision of a financial incentive in the same mailings as the survey itself, and personalized correspondence.
Mr. Nunez pulled out his envelope again, and surveyed his papers one more time.
Continuous envelope data were surveyed using half-overlapping time windows of 300 s.
