Burke's Nth Visitor Methodology (N-Viz™) is used to reduce self-selection bias in surveys of Web site visitors. Burke's N-Viz on Exit^® provides the extra advantage of asking site visitors to participate in a survey as they are leaving your Web site.

The N-Viz application resides on a remote Web site server, counting each visitor and waiting for the nth one to browse the site. When an nth visit occurs, a frame pops into view on a visitor's browser, asking him or her to participate in a survey and offering incentives for doing so.

As is the case with physical-world research, a Web visitor has the opportunity to decline participation. The N-Viz application can, however, reduce the self-selection bias related to obtaining survey responses through simple "click me" buttons. Like those who fill out comment cards by the cash register, respondents to "click me" button surveys are limited to individuals who notice the request and are motivated (positively or negatively) to participate.

N-Viz provides the opportunity to obtain feedback from customers as they arrive at a page on your Web site and can be used for any type of research where a sample of Web site visitors is desired.

For Web site evaluation projects, N-Viz on Exit can provide an even better solution by asking visitors to take a survey after they are done browsing and are leaving your Web site. This application works much like election exit polls, which target every nth exiting voter and solicit his or her participation.

N-Viz on Exit works by first minimizing the survey request page on the visitor's desktop. When the visitor either leaves the site or closes the browser window, the survey request page is maximized. In this way, visitors are not interrupted while they are browsing your site.

Burke works with your technical people to implement N-Viz and N-Viz on Exit. You designate "hot" pages that trigger survey invitations. Depending on the project purpose, these pages might be selected so that visitors invited to surveys are representative of the entire Web site's traffic - or they could be visitors to important niche areas requiring their own research.

The Web server hosting the site is then modified so that visitors destined for the appropriate "hot" pages are sent instead to a remote Burke server, where the N-Viz software resides. This is done through a protocol known as a "CGI (Common Gateway Interface) redirect."

The N-Viz software then determines if the visitor is the nth to arrive since the last survey request was issued. The appropriate value of "n" is chosen based upon traffic volume, the survey participation rate of site visitors and the number of completed surveys required within a given period. If surfers are not the nth visitor, they are sent back immediately to the destination page, and no survey request frame is issued.

When respondents are selected as nth visitors, they also receive cookies. This discourages people from completing surveys twice using the same Internet Service Provider and browser.