A trial is an action which results in one or several outcomes.
An event for an experiment is the collection of some of the outcomes of that experiment.
Experimental probability of an event can be defined as the ratio of the total number of trials favourable to the event and the total number of trials of the experiment.
P(E) = (Total number of trials favourable to the event E) / (Total number of trials of the experiment)
Experimental or empirical probability of an event changes as the number of trials change.
When the number of trials increases the empirical or experimental probability of an event approaches a particular value.
Probability is used for making predictions. Predictions made are based on the analysis of previous data. Some of the fields where probability is used are: physical sciences, commerce, biological sciences, medical sciences, weather forecasting, etc.
Experts in these fields collect various data related to their work and based on that they make forecasts for the future events using probability.
Probability of an event is always between 0 and 1. Mathematically, probability of an event E can be written as:
Event with probability equal to 1 is called the certain event. For example, in tossing a coin getting ‘a head or a tail’ is a certain event.
Event with probability equal to 0 is called the impossible event. For example, in tossing a coin getting ‘two heads’ is an impossible event.