When conducting online surveys, researchers generally want to prevent unauthorized access by:
- Restricting participation solely to those who were invited to respond.
- Allowing each respondent to complete the survey only once.
Here is some practical advice for achieving these important objectives.
Controlling Access
As we saw in “How to find respondents for your online survey (Part 1),” the most common way to deploy an online survey is to send an e-mail to a group of potential respondents asking them to take part in the survey. But how do you restrict access to only those people you invite?
- A common and simple method is to use a nonintuitive web address for the survey. For example: www.domainname.com/09abc12. If this method is used, it is important to exclude the url from the sitemap as well as from both internal and external search engines.
- An additional level of protection is afforded by the use of a password to control access to the survey. Although few of the free or low-cost survey providers offer this functionality, most of the full-featured commercial interviewing systems do. Additionally, the full-featured systems generally allow passwords to be automatically included in with the URLs sent to respondents. This automation eliminates the need for respondents to manually type in a password, so the whole process is seamless to them.
Preventing Multiple Completions
To prevent the same respondent from completing the survey more than once, most full-featured survey systems use cookie-based security (this feature is not included in many free or low-cost survey systems.) To prohibit survey completion by respondents who reject cookies, many researchers have adopted a policy of excluding users who have cookies turned off. This policy should be considered best practice.
An additional benefit of cookie-based security is that it can be set to allow a respondent to exit and resume the survey (for example, if the connection with the server is lost for some reason, the respondent can reenter the survey and pick up right where she left off before the interruption).
The bottom line: when conducting online surveys, it is important to allow only authorized respondents to complete the survey, and to prevent a respondent from taking the survey more than once. Although this is difficult or impossible with many of the free or low-cost survey systems, most full-featured systems not only allow this functionality but also make it seamless to the respondent.
