Non-list based web surveys do not enable unique identifiers, which would enable us to control duplicate entries. Therefore, we have two alternatives, IP address and cookies, however each with certain limitations.
The IP address is a number assigned to all devices logged into the network, including the respondent’s device. 1KA application enables you to block duplication of IP addresses, which can prevent the same person from repeatedly responding to your survey.
This functionality can be accessed under the 'EDIT' - 'Settings' - 'Respondent access' tab. In the ‘Block repeated IP address' category select the desired option - the block can be set to minutes - at least 10, 20 or up to 60 minutes, or to hours - for 12 or 24 hours (this option is off by default).
Limitation: The problem may occur in the case of dynamic IP addresses (dynamic IP address for the same device is changed when disconnected and restored) or in cases where the number of devices on the same network has the same IP address (eg. in organizations).
Despite these limitations, the use of IP blockage may prevent at least some of the simpler frauds like fake responses or server attacks coming from a single device.
A cookie is a small text file sent from the server hosting the web questionnaire and then stored on respondent devices. Next time the respondent visits this same web questionnaire, the 1KA application recognizes this unit, which can be used to prevent repeated access or to enable proper continuation from eventual pausing or breakoff.
1KA application enables a variety of options in terms of cookies, which can be also accessed through the 'EDIT' - 'Settings' - 'Respondent Access':
- 'until the end of questionnaire', means that the cookie is deleted as soon as the respondent finishes answering the survey;
- 'Until the end of the browser session', the cookie is stored for the duration of the browser session (Internet Explorer, Mozilla Firefox, Google Chrome, Opera), i.e. also after the survey is completed and is deleted when respondent closes the browser;
- 'for 1 hour': the cookie is saved for one hour after the respondent first clicked on the survey URL;
- 'for 1 month': the cookie is saved for one month after the respondent first clicked on the survey URL.
You can find more about cookie settings and options for future continuation of the survey fulfilment in the Settings for respondent access: cookies and passwords manual.
Limitation: The problem with cookies is that they are tied to the browser, which means that respondents using another browser, other devices or users deleting the cookie can complete the survey again. Cookies face serious problems due to increasing ethical and legal restrictions, as well as because some users decide to block them. For these reasons, cookies serve poorly as a replacement for the ID code.
In general, we do not recommend using IPs and cookies for restricting access to the survey, because they can cause various expected and unexpected problems. In the default settings of the 1KA application these options are usually turned off. Still, in some specific situations, they can be useful, particularly if we know that in our target population none of the above problems emerges.