Ok, so the point of these quotes was to back up what I've been saying all along, and which you have protested, i.e., that there has to be a specific mechanism which links the probability that a person will volunteer for the test with the characteristic you are testing for there to be a self-selection bias. Personally, I prefer arguments and reason instead of the authority of a book, but since you asked for books, I guess you don't.



I guess this sums it up. If you are now saying that there is a reason to assume a systematic bias in this particular sample, then I can't argue with that, except to say that in my opinion it seems more likely that RJ made a mistake with one of the two numbers, rather than adding a massive bias to those novices as a plot device.

However, I would be very interested (and I'm not being sarcastic, I would actually be very interested) to hear what you think the mechanism of the bias would be.



But in the other post, you agreed that strength in channeling is essentially a random number assigned at birth, unknown until you are tested. I fail to see how this is different from a bunch of people flipping a coin, marking the result without looking at it, and then at some later point volunteering to have their coin tested.

Edit: Fixed a missing quote-tag