Hmm... how would you implement that in this forum?
You can't. At least, not without MAJORLY pissing people off.
The way Self-Selection Bias works is this. Say you're conducting a survey on people's opinions of abortion (or any conroversial topic). If you just put up a survey and say, "Here, if you want to take it, take it," the only people who will take it are those with a strong opinion on the subject. So you'll get a lot of extreme opinions on both sides, and almost nothing in the middle. Whereas if you actually say, "Alright, we're asking these specific 50 people what they think," you force the moderates you randomly selected to make themselves heard. In this case, you'll have a much more normal distribution, with a lot of opinions in the middle and very few extremes.
