Some things I cannot change

I may be misunderstanding, because me and science and statistics have never been on very close terms, but as far as I can tell, this story, about how1 in 25 fathers may be unknowingly raising another man's child, is based on data gathered from people who had paternity tests done, right? So for a fair number of them, there were doubts in the first place, or they wouldn't have been testing. And .. no one thought that perhaps, just perhaps, that might skew the results a tiny bit?

ETA: Also, for those who are interested - the pilot of Lost got over 6 million viewers last night. Rock on.