Probability deals with uncertainty. In mathematics this process is called as probability. In our daily life, while speaking we use words like likely, possibly, probably.

**For example:**

- Probably, I may go to a movie.
- He is likely to get the prize.
- Possibly, Kam may be leave today.

What does the word likely, possibly, probably convey? It conveys that the event that we take under consideration may happen or may not happen. It is the case of uncertainty.

Introduction to probability and probability terms:

The meaning of the word probable in dictionary says “likely but not certain”. So we could say probability as an index which numerically measures the degree of certainty or degree of uncertainty in the occurrence of events. To learn about the definition of probability, it is very essential to know about the terms involved in probability.

Terms in Probability:

**Experiment:** An activity which results in a well defined outcome is called an experiment.

**Random experiment:** An experiment in which all possible outcomes are known in advance, but the exact result of any trial cannot be surely predicted is called random experiment. Tossing a coin, throwing a die, picking a ball from a bag of balls are examples for random experiment

**Trial:** Performing an experiment once is called a trial

**Events:** The possible outcomes of a trial are called events.

**Equally likely events:** If the different outcomes of a trial have equal chance of occurring, then outcomes are said to be equally likely.

For example: when we throw a dice once, the chances of 1, 2, 3, 4, 5, 6 occurring is the same. So they are equally likely to appear.

**Sample space:** The set of all possible outcomes of an experiment, constitute its sample space.

**Dependent Events:** Occurrence of one event does have an effect on the probability of second event.**Independent Events:** Occurrence of one event has no effect on the probability of second event.**Outcome: **Each result of a trial is called outcome.

Types of probability

There are two types of probability. They are theoretical Probability and Experimental or Empirical probability

**Theoretical probability:** The mathematical chance of occurrence of an event according to the law.

Probability = $\frac{Number\ of\ outcomes\ favourable\ to\ an\ event}{Total\ number\ of\ possible\ outcomes}$

**Experimental probability:** When the number of cases favorable to an event is found out experimentally and then the probability is calculated, that is called experimental probability of an event.

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