1. The random variable Y=Y(w) is defined to represent the number of extracted defective products. This is actually knowing the range and finding the domain, but the domain here is an event, not a real number. Y=Y(w) is a real function and a range, which can be larger or smaller than a certain number.

2.X(w) is actually x, and w is removed only for writing convenience. X is a real number, and the random variable X has a value range, which is determined by the sample point W. X has no value range, but X may not get the value of X.

3. See the answer of 1 for the question of evaluating a domain by defining it.