You forget to set your alarm with a probaility of .3. If you set the alarm it rings with the probabilty of .8. If the alarm rings, it will wake you on time to make your first class with the probability of .9. If the alarm does not ring, you wake in time for your first class with a probability of .2. What is the probabiltity that you wake in time to make your first class tomorrow?

Answer 1

Pr= get to school|didnt ring * pr didn't ring + get to school|did ring * pr did ring

Pr= .8*.9 + .3*.2= .72+.06