Regarding visitors self-selecting to fill out a computerized survey:
We looked into this a couple of years ago.  There are a number of
companies offering these services, either by lease or purchase, because
the staff cost of human interviewers and data entry can be prohibitive,
especially for long term or large studies.

I checked with a visitor studies consultant we used and he had serious
questions about the bias a couple of the comments have mentioned.  One
solution the vendor offered, that is in use at some museums, is to use a
combination.

Have the survey on computer,  with automatic data entry, and use a staff
person to randomly (or non-randomly if that's what your survey requires)
solicit visitors to take part and note refusal rates and types.  T

hat way, by comparing to standard visitor demographics, the researcher
can weight to compensate for undersampled segments.

I don't remember the name of the company, but I can search for it.  As I
recall they were not offering the most sophisticated of survey
techniques and research help so you might want to start new.

Linda Wilson
Visitor Studies & Evaluation
John G. Shedd Aquarium
Chicago, IL  60640
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