To control the success of your promotion strategies you could ask participants
to specify how s/he came to that online study. With JavaScript,
PHP or Perl it is possible to record (in the background, without the user's
knowledge) the webpage that the user had
visited before s/he came to the study. If you are not sure, whether user's
browser can supply you with the information you can simply ask, e.g. How did
you find out about our study?
Reference as a drop-down menu
With drop-down menus one can save a lot of space and kinda pretend to have a short
survey. However, one should still be careful applying drop-down menus and consider that a user needs more time to choose the appropriate answer in a drop-down menu than in choosing the right radio button or a check box. In some cases drop-down menus
are, on the other hand, the only choice, especially when the list of possible answers to choose from is rather
long. From cognitive psychology we know that the human being is able to comprehend up to six elements at the same time, hence drop-down menus should only be used with more than 7 possible
answers.
