Page 1 - Lesson Notes-Probability

SAI International School
CLASS - IX

Mathematics
CHAPTER-15: PROBABILITY

Lesson Notes-1
SUB-TOPIC: INTRODUCTION:
PROBABILITY
Probability is the special branch of Mathematics which measures the degree of
‘uncertainty’ numerically. It is the study of uncertainty of any doubtful situation.
Uses of Probability
Probability is used in many fields like Mathematics, Physical
Sciences, Commerce, Biological Sciences, Medical Sciences, Weather
Forecasting etc.
Basic terms related to Probability
1. Random Experiment
An experiment which when performed produces one of the several
possible outcomes is called a random experiment.
For Example : In the tossing of a coin one is not sure if a Head or Tail will be
obtained, so it is called a random experiment.
Similarly, rolling an unbiased die is an example of a random experiment.
Or In other way, we say
If we are doing an experiment and we don't know the next outcome of the
experiment to occur then it is called a Random Experiment.

2. Trial

A trial is that action which results one or more outcomes.
Examples - Like throwing of a dice, tossing of a coin, playing a card etc.

3. Independent trial
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