A sample is any collection of observations from an experiment. The population is the collection of all possible results from an experiment. You can think of the samples as a list of events from the sample space. Mathematically, a sample $S=\left[E_1,\dots,E_n\right]^T$ is an element of $\Omega^n$. If repeated trials in the sample space $\Omega$ can be modeled by a sequence of