what is the addition rule for probabilities 
the addition rule for probabilities describes two formulas one for the probability for either of two mutually exclusive events happening and the other for the probability of two non mutually exclusive events happening the first formula is just the sum of the probabilities of the two events the second formula is the sum of the probabilities of the two events minus the probability that both will occur the formulas for the addition rules for probabilities ismathematically the probability of two mutually exclusive events is denoted by p y or z p y p z p y text or z p y p z p y or z p y p z mathematically the probability of two non mutually exclusive events is denoted by p y or z p y p z p y and z p y text or z p y p z p y text and z p y or z p y p z p y and z 