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Let Ω={ω1​,ω2​,…,ωN​} be a finite set of exactly N points, and let F be the power set of Ω. It is easy to check that the function P defined by P(A)=1/N​∣A∣ for A∈F is a probability measure on (Ω,F)⁵

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We're tasked with finding the probability measure of a set A within our finite set of N points.

Step 1: Define Your Sets
First, we recognize that Ω={ω1​,ω2​,…,ωN​} is a finite set of exactly N points. The power set F is simply all possible subsets that can be made from Ω, and A is one of those subsets.

Step 2: Calculate the Size of A
To find the probability measure of A, we first need to calculate the size of A, which is simply the number of elements in subset A. This can be denoted as |A|.

Step 3: Apply the Probability Measure Formula
The probability measure P(A) is calculated as 1/N​ * |A|, where N is the number of elements in the original set Ω and |A| is the number of elements in subset A.

This formula essentially divides the size of our subset A by the size of our original set Ω to find the probability measure of A.

So, to find the probability measure of A, simply count the number of elements in A and divide by the total number of elements in Ω (N). This will give you the relative size of A within Ω, which is the probability measure we're looking for.

To summarize:
The formula P(A)=1/N​ * |A| will calculate the probability measure of any subset A in the power set F of a finite set Ω of N points. The size of A (|A|) is the number of elements in A, and N is the number of elements in the original set Ω. This probability measure essentially tells us the relative size of A within Ω.

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