Ex-Post-Facto Statistics
Ex-post-facto statistics search the data after the fact for a pattern and then present it as if it had been predicted. Debaters answer by pointing out that a pattern found only by looking back at the results is likely to be chance.
Ex-Post-Facto Statistics as it appears in championship debate rounds. Each example below is a moment from a real round, with a note on why it illustrates the technique and how a debater can use it, or answer it.
Example 1
The speaker multiplies odds after the fact (1 in 20,000 that your parents meet, 1 in 400 quadrillion for the exact egg and sperm) to argue that human existence is astonishingly unlikely. Working out the probability of one specific outcome only after it has happened makes any outcome look impossible, so the speaker commits ex-post-facto statistics. When an opponent leans on after-the-fact odds, point out that some specific outcome had to occur, so its low prior probability proves nothing special.
Sources: every example links to the YouTube video of the championship debate it comes from, at the moment described.
All techniques and fallacies