### Probability - Revision Notes

CBSE Class 09 Mathematics

Revison Notes
Chapter 15
PROBABILITY

• Probability – An Experimental Approach
1. Experiment - A procedure which produces some well defined possible outcomes..
2. Random experiment - An experiment which when performed produces one of the several possible outcomes called a random experiment.
3. Trial - When we perform an experiment it is called a trial of the experiment.
4. Event - The set of outcomes of an experiment to which probability is assigned.It is usually denoted by capital letter of English alphabets like A, B, E etc.
5. A collection of two or more possible outcomes (elementary events) of an experiment called a compound event.
6. An event is said to be happen in trial if any one of the elementary events (or outcomes) satisfying its conditions is an outcome.
7. The empirical (or experimental) probability P(E) of an event E is given by $P\left(E\right)=\frac{Number\phantom{\rule{thickmathspace}{0ex}}of\phantom{\rule{thickmathspace}{0ex}}trials\phantom{\rule{thickmathspace}{0ex}}in\phantom{\rule{thickmathspace}{0ex}}which\phantom{\rule{thickmathspace}{0ex}}E\phantom{\rule{thickmathspace}{0ex}}has\phantom{\rule{thinmathspace}{0ex}}happend}{Total\phantom{\rule{thinmathspace}{0ex}}no.\phantom{\rule{thinmathspace}{0ex}}of\phantom{\rule{thickmathspace}{0ex}}trial}$
8. The probability of an event lies between 0 and 1 (0 and 1 are included)
9. Impossible event: Event which never happen.
10. Certain event - event which definitely happen.