Sample size is important because
(1) sample size includes all possible outcomes
(2) it also includes number of favourable outcomes
for finding probability , we use formula
probability= ( number of favourable outcomes)/(total number of possible outcomes)
We can get both in sample size
it will help us to find probability
For example:
If a dice is rolled , we get sample space
sample space = { 1 , 2, 3, 4, 5, 6}
Suppose, we want to find probability of getting even number
so, favourable outcomes = {2,4,6}=3
total number of possible outcomes={1,2,3,4,5,6}=6
so, probability = 3/6 =1/2