Alice's idea is better. Bob's idea is better. Both approaches are equally good. Heads comes up more often than tails. Heads comes up at least twice.
Tails comes up exactly once.
The whole sample space. In order to calculate probabilities of complex events, one needs to be aware of the probabilities of simple events. 0.4 0.5 0.6 0.7 0.8 0.9 Roy is making plans for the evening. He can watch a movie, go to a bar, or study for the MATH250 test. He is twice as likely to watch a movie than to go to a bar, and equally likely to watch a movie as he is to study for the test.