PROBABILITY
Frequently Asked Questions
Probability is a numerical measure of the likelihood of an event, defined as \(P(E)=\frac{\text{Number of favourable outcomes}}{\text{Total number of equally likely outcomes}}\).
An experiment is a process whose outcome cannot be predicted with certainty in advance.
The sample space \(S\) is the set of all possible outcomes of an experiment.
Any subset of the sample space is called an event.
If all outcomes are equally likely, then \(P(E)=\frac{n(E)}{n(S)}\).
A random experiment is one whose result cannot be predicted with certainty but has well-defined possible outcomes.
Outcomes having the same chance of occurrence are called equally likely outcomes.
An event that always occurs has probability \(1\).
An event that never occurs has probability \(0\).
For any event \(E\), \(0\le P(E)\le1\).
If \(E\) is an event, then its complement is \(\bar E\), where \(P(\bar E)=1-P(E)\).
\(P(S)=1\).
\(P(\phi)=0\).
An event containing only one outcome is called an elementary event.
An event containing more than one outcome is called a compound event.