The least value of probability is 0, it means that
the probability of occurring the event is completely impossible. And
the highest value of probability is 1 that means the
probability of occurring the event is certain. In this way, the
probability of getting any event E lies between 0 and 1, i.e.,
0 ≤ P(E) ≤ 1. It is called a
probability scale.
Add all the probability after finding the probability.
P(H) =
12
or, P(T) =
12
P(H) + P(T) =
12
+
12
= 1
Similarly, what is the probability of not occurring H and T?
Showing the above probability in number line as:
0
Probability of not getting both H and T
1⁄2
Probability of getting any one of H and T
1
Probability of getting H or T
We can conclude as following based on the above number line
Probability of getting H or T: P(H) = P(T) =
½
Probability of getting in tossing a coin H or T: P(H or T) =
½ + ½ = 2/2 = 1
P(S) = 1 where S = {H, T}