I've seen so many exchanges on the Internet lately that go like this:
Smart person: You know, research shows that the older the mother gets, the more likely the children are to have Down's Syndrome.
Lefty: So what? More Down's Syndrome babies are born to young mothers.
I guess leftists are too busy learning at racist studies programs from Marxist professors to take classes in basic math and science, or else they'd not make a statement that so blatantly shows a lack of understanding of basic probability.
Hint to the lurker trolls: Thomas Bayes has the droids you are looking for. You see, Bayes did some work with respect to conditional probabilities, showing the way those probabilities change given the addition of new data.
I'll spare the mathematical details, but consider this hypothetical. There are two coins: One has a head and a tail, and one has two heads (it's used to cheat). Your 'buddy' grabs a coin and is going to flip it. What's the probability that he picked each coin? 50% each. Easy.
But what happens when he starts flipping the coin? If after the first flip it's tails, then obviously it's not the two-headed coin. The probabilities are 100% (normal) and 0% (two-headed). That's easy. After one heads toss, the probabilities are about 33% (normal) and 67% (two-headed). After two heads tosses, they become 25% and 75%. These can be calculated, as I just did, by counting outcomes and doing division.
However what Thomas Bayes did was to do the math for more complicated cases. Using the principle of Bayes' rule one could take the probability of Trig Palin being the child of Bristol Palin or Sarah Palin, plug in the the fact that Trig Palin has Down's, and get an increased probability that Sarah truly is the mother. No, it doesn't matter that more Down's children are born to young mothers. What matters is the probabilities are changed. Given what we know about Trig Palin, basic probability states that Sarah Palin is more likely to be his mother than if we didn't know anything about him.
So you can go about your business. Move along. Or not, because the more you push this, Obama fans, the more you 'prove' to the PUMAs that Obama hates strong women, so much that he'll use any insinuations he can about hysterics, PMS, or anything else in order to be top.