# Definition of Probability

We will discuss here about the definition of probability, terms

related to probability, experiment, random experiment and trial.

**Introduction**

We often hear sentences like “it will possibly rain today”, “most

probably the train will be late”, “most likely Robert will not come today”,

etc.

In saying such sentences we try to measure the uncertainty

of an event (incidence).

In the study of probability, we try to measure numerically the

chances that favor the occurrence of an event.

The theory of probability originated from gambling. But at present this theory is so developed that it is being used in many fields of knowledge like economics, industry, engineering, navigation and defence. Some of the mathematicians who made considerable contribution to the development of the theory of probability are Blaise Pascal (1623 – 1662), Pierre de Fermat (1601 – 1665), Jacques Bernoulli (1654 – 1705), Abraham de Moivre (1667 – 1754), Simeon Dennis Poisson (1781 – 1840), Pafnuty Chebyshev (1821 – 1894), Andrei Markov (1856 – 1922) and Andrei Kolmogorov (1903 – 1987).

Terms Related to Probability:

**Experiment:** An action or process that results in well-defined

outcomes is known as an experiment.

**Example:** The toss of a coin is an experiment because it

results in a “head” or “tail”. So, the outcomes are well-defined.

**Random Experiment:**

If an experiment, although conducted

under identical conditions, can result in two or more known outcomes, it is

called a random experiment.

**Trial:**

The process of conducting an experiment is called a

trial which results in any one of the possible outcomes.

Definition of Probability:

The concept of probability

started in a statistical form of collecting data and it was called Empirical

Probability. Later a theoretical approach was introduced for probability and it

was called Theoretical Probability or Classical Probability.