Probability theory and distribution function of random variables in mathematical statistics Let the distribution law of random variable X be X -1 2 3 p 0.25 0.5 0.25 Finding P {2 ≤ x ≤ 3} through the distribution function of X The solution is p {2 ≤ x ≤ 3} = f (3) - f (2) + P {x = 2} I want to ask why we add "P {x = 2}" and what is the relationship between the equal sign of 2 ≤ x ≤ 3

Probability theory and distribution function of random variables in mathematical statistics Let the distribution law of random variable X be X -1 2 3 p 0.25 0.5 0.25 Finding P {2 ≤ x ≤ 3} through the distribution function of X The solution is p {2 ≤ x ≤ 3} = f (3) - f (2) + P {x = 2} I want to ask why we add "P {x = 2}" and what is the relationship between the equal sign of 2 ≤ x ≤ 3

The owner may not know the definition of distribution function
F（x）=P{X≤x}
So p {2 ≤ x ≤ 3} = P {2}