Probability and It’s
Charecteristics
Probability is a numerical measure of the likelihood that a specific event will occur.
There are two properties of probability. The explanation are given bellow-
First Property: The probability of an event always lies in the range 0 to 1.
It
simply means that, whether it is simple or a compound event, the probability of
an event is never less than zero or greater than one.
Mathematically
implies that-
0 ≤ P(Ei) ≤1; For Simple event
0 ≤ P(A) ≤1; For Compound event
What does mean impossible event or sure event?
An
event that can not occur has zero probability; such an event is called an
impossible event. For example: If we roll a die, we will never get number 7 and
the probability of showing up number 7 is '0'.
An
event that is certain to occur and the probability is equal to 1 is called a
sure event.
For
example:
Universal truth event.
Mathematically implies that-
For
an impossible event M: P(M)=0
For
a sure event C: P(C)=1
Second Property:
The
sum of the probabilities of all simple events for an experiment is always 1.
Mathematically
implies that-
∑P(Ei)=P(E1)+P(E2)+P(E3)+…..=1
For
example:
For
the experiment of one toss of a coin.
P(Head)+P(Tail)=1
What does mean the valid or invalid probability?
For
a valid probability distribution, an event must be follow the two
charecteristics of probability as i mentioned above.
For
an invalid probability distribution, an event either follow any one
charecteristics or doesn't follow or maintain the two properties of
probability.


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