Mathématiques · Glossaire
What is Probability?
Définition rapide
A measure of how likely an event is, between 0 (impossible) and 1 (certain). Often expressed as a percentage.
Explication complète
Probability quantifies the likelihood of an event on a scale of 0 (impossible) to 1 (certain). 0.25 means a 25% chance. Probability theory has three axioms: 1) P(event) ≥ 0, 2) P(certain event) = 1, 3) P(union of disjoint events) = sum of P. Key rules: P(A and B) = P(A) × P(B) for independent events. P(A or B) = P(A) + P(B) − P(A and B). Conditional probability P(A|B) updates beliefs given new information. Bayes' theorem formalizes this. Probability underlies statistics, gambling, insurance, finance, machine learning, and quantum mechanics. Frequentist and Bayesian interpretations differ philosophically.
Calculatrices liées
Calculators that use or explain Probability.
Termes liés
More from Mathématiques
Standard Deviation
A measure of how spread out numbers are from their mean. Low = consistent, high = volatile.
P-Value
The probability of observing results at least as extreme as those observed, assuming the null hypothesis is true.
Mean (Average)
The sum of values divided by the count. The most common type of "average." Sensitive to outliers.
Median
The middle value in a sorted list. Half the values are above, half below. Robust to outliers.
Pythagorean Theorem
In a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs: a² + b² = c².
Logarithm
The exponent to which a base must be raised to produce a given number. log(100) = 2 means 10² = 100.
Last reviewed: June 15, 2026 • Category: Mathématiques