Come on, we’re scientists, right? How about we break out the mathematics. Just for kicks, I’m gonna model Coulter as a Bernoulli process!
Assume, as a first approximation, that each statement she makes has probability p of being worth reading. (This could be because it is factually correct, poetically beautiful, intellectually thought-provoking, etc.) Furthermore, assume that this probability does not change significantly over time, and that one statement does not affect the others. Then out of every N statements, on average Np of them will not have been a waste of time — though in any actual sample of N statements, the number will likely be somewhat different, just as not every set of 100 coin flips will give you exactly 50 heads.
Given a sample of statements which we judge to be worthwhile or worthless, what can we say about p, the “behind the scenes” probability that the source will produce a worthwhile statement?
Say that we actually do the experiment: we take N statements from Coulter’s books, TV appearances and so forth, and we find that some fraction q of them were not blatant assaults upon human dignity. That is, Nq statements did not reek of idiocy and hate. Knowing N and q, we would like to deduce p to within some reasonable margin of error.
Standard scientific practice requires that we set a “confidence level“, which measures how far our results are from certainty. A confidence level of 95% means that our results will only be wrong 1 time in 20, all else being fair. You can look up the rest in Chapter 7 of Gonick and Smith’s Cartoon Guide to Statistics; the punchline is that the width of our “error bar” is (for 95% confidence) 1.96 times the square root of the fraction q(1-q)/N. The probability we want to know, p, will be q “plus or minus” that amount. Our confidence in our answer grows as the square root of the number of measurements we take: for a sample twice as large, our uncertainty becomes about 1.4 times smaller.
For example, if 800 out of 1000 statements are total bollocks, then p = 0.2 +/- 0.02.
Now all you have to do is decide how small p has to be before you stop listening and go do something more fun.