The test is deemed controversial in some research circles, because it is being conducted live on Nielsen's national TV ratings sample, and theoretically could impact the stability of Nielsen's core TV research. But Nielsen executives have maintained that the impact of measuring both TV and online behavior in a small subset of its sample households would be minimal, and that they would monitor the situation closely to ensure there is no impact on the quality of its national TV ratings.

"Maintaining the integrity of our currency panels will remain a top priority throughout the test," Nielsen said in an update sent to clients on Monday. Nielsen's initial goal is to begin measuring TV and Internet usage in 375 of its people meter sample homes before making a decision this fall to expand it.

One concern some researchers have had about the program is the reluctance some households might have to sharing their online usage behavior with Nielsen, but Nielsen said the inclusion of Internet measurement would be optional, and that any households that declined it would still be eligible to participate in its conventional TV audience measurement panel.

For those households who agree to participate in the integrated measurement, Nielsen said it would simultaneously measure their TV viewing, along with both Internet video consumption and Web site navigation.

"Recently, there has been renewed industry discussion around the idea of making traditional television programs and commercials available on the Internet," Nielsen noted in Monday's update. "These developments make this test and its timing all the more relevant as it will build a foundation for the inclusion of online viewing in our television currency. While there is much work to do before we can achieve that goal, this will allow us to accelerate the process of launching integrated measurement of television and Internet video in our People Meter panels, as client needs emerge."

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