Which bag?
Start from how common something is, then adjust for what you see. And a streak of luck usually ends.
5 minutes · trains Weigh odds · points only, never money
Two short games about judging chances. First, guess which kind of bag a ball came from, and say how sure you are. Then back a player for the next round after seeing one round of scores.
Part 1: which bag?
There are 10 bags of 10 balls. 8 are mostly red: 7 red balls and 3 blue. 2 are mostly blue: 3 red and 7 blue.
Each round a bag is picked at random, and one or two balls are drawn from it, each put back before the next. Say which kind of bag you think it was, and how sure you are. Eight rounds.
Then part 2: ten players, one lucky round, and a pick for the next.
Try it yourself
1 person in 100 has a condition. A test finds 9 in 10 people who have it, and wrongly flags 1 in 10 who do not. Someone tests positive. How likely is it they have it?
3 questions, a minute or two. Nothing to finish first.
Want more? Practise Weigh odds.
Read more
- Start from the base rate Before judging one case, ask how often cases like it turn out each way. Start from that, then adjust for what this case shows.
- Regression to the mean When a result is part skill and part luck, an extreme result is usually followed by a more ordinary one, whatever you do.
- The Weigh odds course Lessons and practice for the skill this lab trains.