Probability: Numerical Likelihood of an Event
Probabilities
Probability: Numerical likelihood of an event
Probability value of 0 – 1, higher values describes a greater chance the event will occur
Classical Interpretation
Equally likely outcomes, probability is divided by the total number of possible outcomes
Frequentist Interpretation
If a process to obtain the probability was repeated in similar conditions a number of times, the probability is the relative frequency of all the tries
Subjective Interpretation
Someone’s degree of belief in the occurrence of the event is the subjective probability
Probability of event occurring : probability of event not occurring
e.g. Mrs X will survive 5 years: odds of 4 to 1 = probability (survive 5 years) 4/Probability (die within 5 years) 1 = 4/1
Odds >1 (greater than 1) then event is more likely to occur
Odds <1 (less than 1) then event is less likely to occur
To convert odds to a probability:
e.g. Odds of 4 to 1
Probability (event) = A / A+B (A = 4, A + B = 4 + 1)
To convert probability to odds:
A = p/1-p (p = probability)
Not Events
A probability than an event does not occur
Probability (event does not occur) = 1 - Probability (event occurring)
Or Events (Addition