Hi.  We at ISO always offer respondents a gift.  These gifts have typically
been inexpensive but unique trinkets, buttons, pencils, bookmarks,
postcards, posters, etc.  In one case we offered respondents a 10% discount
to the museum shop.

We offer these trinkets as thanks for participation and do not mention
them during the interview.  Organizing the interview around compensation
will tend to bias your sample, by including more people who want the freebee.
If you are offering the incentive as a way to improve response rates,
please take the money and it use to hire and train competent interviewers.
A good interviewer can collect data from reluctant visitors without
damaging your sample.  Use the "incentive" as a token of thanks, not as
a way to coerce visitors into answering your questions.

 --Cheers, Adam Bickford

Adam Bickford, Smithsonian Institution,
Institutional Studies Office:: [log in to unmask]
(202) 786-2289