We have a coin that is heads-only with probability 20%, and fair with probability 80%. We’ve already conducted exactly one flip of this coin, which came out heads (causing out update from the prior of 10/80/10 to 20/80/0), but no further flips yet.
For simplicity, event A will be “heads on next toss” (toss number 2), and B will be “heads on toss after next” (toss number 3).
It’s awful that you were downvoted in this thread when you were mostly right and the others were mostly wrong. I’m updating my estimate of LW’s average intelligence downward.
Please actually do your math here.
We have a coin that is heads-only with probability 20%, and fair with probability 80%. We’ve already conducted exactly one flip of this coin, which came out heads (causing out update from the prior of 10/80/10 to 20/80/0), but no further flips yet.
For simplicity, event A will be “heads on next toss” (toss number 2), and B will be “heads on toss after next” (toss number 3).
P(A) = 0.2 1 + 0.8 0.5 = 0.6 P(B) = 0.2 1 + 0.8 0.5 = 0.6
P(A & B) = 0.2 1 1 + 0.8 0.5 0.5 = 0.4
Note that this is not the same as P(A) P(B), which is 0.6 0.6 = 0.36.
The definition of independence is that A and B are independent iff P(A & B) = P(A) * P(B). These events are not independent.
Turning the math crank without understanding what you are doing is worse than useless.
Our issue is about how to understand probability, not which numbers come out of chute.
It’s awful that you were downvoted in this thread when you were mostly right and the others were mostly wrong. I’m updating my estimate of LW’s average intelligence downward.