Here I have a couple of urns. The one on the left contains 70 red balls and 30 black. The one on the right contains 30 red and 70 black.
While you weren’t looking, I reached into one of these urns and randomly drew out a dozen balls. As you can see, 4 of them were red and 8 were black.
Here are three questions that I think you ought to be able to answer if you want to be in the business of assessing evidence:
- If you had to guess, which urn would you guess I drew from?
- What’s your estimate of the odds that you’re right?
- Do you think you’re right beyond a reasonable doubt?
Further discussion to follow later in the week. (Hat tip to Howard Raiffa, who will also figure in the upcoming discussion.)