題組內容

4. (10%) Suppose that 500 points are selected independently and at random from the unit square 

$\{(x, y): 0 \le x < 1, 0 \le y < 1\}.$
Let W equal the number of points that fall into $\{(x, y): x^2 + y^2 < 1\}$.

(a) (5%) Write down the distribution of \( W \) and the corresponding probability mass function.