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The probability based on an event that has already occurred is 100%. If the event has occurred, it has occurred.

Q: What is a probability based upon an event that has already occurred?

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The probability of event A occurring given event B has occurred is an example of conditional probability.

The likelihood of an event occurring is known as the probability of occurrence. This can be calculated based on previous patterns and other factors.

The probability of an impossible event is 0.The probability of an impossible event is 0.The probability of an impossible event is 0.The probability of an impossible event is 0.

Addition Theorem The addition rule is a result used to determine the probability that event A or event B occurs or both occur. ; The result is often written as follows, using set notation: : ; where: : P(A) = probability that event A occurs : P(B) = probability that event B occurs : = probability that event A or event B occurs : = probability that event A and event B both occur ; For mutually exclusive events, that is events which cannot occur together: : = 0 ; The addition rule therefore reduces to : = P(A) + P(B) ; For independent events, that is events which have no influence on each other: : ; The addition rule therefore reduces to : ; Example ; Suppose we wish to find the probability of drawing either a king or a spade in a single draw from a pack of 52 playing cards. ; We define the events A = 'draw a king' and B = 'draw a spade' ; Since there are 4 kings in the pack and 13 spades, but 1 card is both a king and a spade, we have: : = 4/52 + 13/52 - 1/52 = 16/52 ; So, the probability of drawing either a king or a spade is 16/52 (= 4/13).MultiplicationTheorem The multiplication rule is a result used to determine the probability that two events, A and B, both occur. The multiplication rule follows from the definition of conditional probability. ; The result is often written as follows, using set notation: : ; where: : P(A) = probability that event A occurs : P(B) = probability that event B occurs : = probability that event A and event B occur : P(A | B) = the conditional probability that event A occurs given that event B has occurred already : P(B | A) = the conditional probability that event B occurs given that event A has occurred already ; For independent events, that is events which have no influence on one another, the rule simplifies to: : ; That is, the probability of the joint events A and B is equal to the product of the individual probabilities for the two events.

The probability of the complement of an event, i.e. of the event not happening, is 1 minus the probability of the event.

Related questions

100% it already happened

May - or may not - be a conditional probability. A conditional probability is not becessarily chronologically structured.

It can be called a "conditional probability", but the word "conditional" is irrelevant if the two events are independent.

If the event has already happened, then the probability is 100%.

The two events are said to be independent.

The probability of event A occurring given event B has occurred is an example of conditional probability.

Historical events which have occurred have a probability of 1. They are a certainty. This refers to the event itself, not some historian's or politician's interpretation of what happened. However, the probability that they will occur again depends on the event. Exact recurrence is impossible (probability = 0).

no

In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.

The likelihood of an event occurring is known as the probability of occurrence. This can be calculated based on previous patterns and other factors.

The probability of an impossible event is 0.The probability of an impossible event is 0.The probability of an impossible event is 0.The probability of an impossible event is 0.

this is called a a posteriori probability. based on some evidence, you are trying to estimate the likelyhood of the hypothesis.