Probability Calculator

Use

You can use a probability calculator to determine the likelihood of a single occurrence or a series of related events. Simply choose an event and enter your values to get the likelihood. Single.

The Chance of Two Events
Probability is a way to gauge how likely something is to happen. It is expressed as a number between 0 and 1, with 1 denoting certainty and 0 denoting the impossibility of the event. It follows that the likelihood of an event increasing increases with probability, making its occurrence more likely. Probability can be expressed mathematically in the most generic sense as the ratio of desired outcomes to total outcomes. This is further influenced, among other things, by whether the events being investigated are independent, mutually exclusive, or conditional. The calculator computes the likelihood that event A or B does not occur, as well as the likelihood that A or B occurs when the two do not coincide.

Combination of A and B
It is easy to determine the complement, or the likelihood that the event indicated by P(A) does not occur, P(A'), given a probability A, denoted by P(A). If, for instance, P(A) = 0.65 denotes the likelihood that Bob will not complete his schoolwork, his teacher Sally can forecast the likelihood that Bob will do it as follows:

P(A') = 1 - P(A) = 1 - 0.65 = 0.35

Therefore, there is a 35% likelihood that Bob completes his assignment in light of this circumstance. Any P(B') would be computed in the same way. It's important to note that in the calculator above, P(B') can be independent, meaning that if P(A) = 0.65, P(B') doesn't necessarily have to equal 0.35 but might also equal 0.30 or another value.

Crossing of A and B
The combined probability of at least two occurrences is represented below in a Venn diagram as the intersection of events A and B, also written as P(A B) or P(A AND B). P(A B) = 0 when A and B are occurrences that cannot both occur at the same time. Take into account the impossibility of rolling both a 4 and a 6 on the same die. Therefore, these occurrences would be thought to be mutually exclusive. If the occurrences are independent, computing P(A B) is easy. The likelihood of events A and B in this situation are doubled. To determine the likelihood that two different die rolls result in 6 each time:

The supplied calculator takes into account the scenario when the probabilities are