PROBABILITY MODELA probability model for a random processdescribes all the possible outcomes and sayshow to assign probabilities to any collection ofoutcomes.Flip a coinHTProbability0.50.5
PROBABILITY RULE AAny probability is a number between 0 and 1.A probability can be interpreted as theproportion of times that a certain event can beexpected to occur.If the probability of an event is more than 1,then it will occur more than 100% of the time(Impossible!).
PROBABILITY RULE BAll possible outcomes together must haveprobability 1.Because some outcome must occur on everytrial, the sum of the probabilities for all possibleoutcomes must be exactly one.If the sum of all of the probabilities is less thanone or greater than one, then the resultingprobability model will be incoherent.
PROBABILITY RULE CThe probability that an event does not occur is1 minus the probability that the event doesoccur.As a jury member, you assess the probabilitythat the defendant is guilty to be 0.80.Thusyou must also believe the probability thedefendant is not guilty is 0.20 in order to becoherent (consistent with yourself).