Page 4 - Lesson Notes-Probability

Sure or Certain Event
While doing an experiment, if there is surety of an event to happen then it is said to
be the sure event or certain event. Here the probability is one (1).
It is certain to draw a blue ball from a bag contain blue balls only.

This shows that the probability of an event could be 0 ≤ P (E) ≤ 1.

Probability Line

We can show probability on a Probability Line:

Probability is always lie between 0 and 1.

Example -3

Two coins are tossed simultaneously 500 times, and we get
Two heads :105 times, One head: 275 times, No head :120 times
Find the probability of occurrence of each of these events.

Solution:
Total number of tosses = 500
105
P (Two heads)= = 0.21
500

275
P (One head) = = 0.55
500

120
P (No head) = = 0.24
500

Therefore,
105 275 120
P (Two heads) + P (One head) + P (One head) = + + = 1
500 500 500

CONCLUSIONS:

1.The probability of each event lies between 0 and 1
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