The question is based on the following problem in the book Probability Essentials by Jacod:
Here is my question:
What does $P(\{k\})$ mean in the second problem?
The probability on a finite or countable measurable space $(\Omega,\Sigma)$ is determined by $P(\{\omega\})$ where $\omega\in\Omega$. As I understand, for the binomial distribution $B(p,n)$ the sample space is $\Omega=\{(a_1, a_2):a_1,a_2=0,1\}^n$. How does $P(\{k\})$ come out here?