Using cookies to identify respondents
The ability to set the way Vista identifies respondents is a valuable feature. It also is a necessary one because it affects the way Vista enforces the Security tab setting When a respondent takes your survey a second time.
Click the Security tab. Under Identify repeat respondents by, select Persistent cookie or IP address.
The default and recommended setting is Persistent Cookie which will use a unique, persistent cookie written to the user's computer to identify the user on return visits to the survey. Unfortunately, if the respondent has disabled cookies in his Web browser, Vista will not be able to prevent that respondent from taking your survey again. However, it is not typical to have cookies disabled.
Always use the Persistent cookie setting if you are not familiar with how IP addressing works.
Do not select the IP address option if you are sending an employee survey or any survey within your company.
Using the respondent's IP address as an identifier is more restrictive than cookies; however, many company networks are set up to allow users to share addresses. Also, with some ISPs, a user can have a different IP address each time they log in. Vista communicates with your company's network from outside of your company and is only able to identify one IP address for all of your employees. If you select IP address, then every survey submission will overwrite the last submission unless you have also selected the setting Allow the respondent to take the survey as many times as they want and keep all results under When a respondent takes your survey a second time.
NOTE: If you send your email invitations through Vista, the Identify repeat respondents by setting does not apply because Vista is able to track the respondent using the unique link in the invitation email.