• The probability distribution of a discrete random variable \(X\) is a listing of each possible value \(x\) taken by \(X\) along with the probability \(P(x)\) that \(X\) takes that value in one trial of the experiment. 
  • The mean \(\mu\) of a discrete random variable \(X\) is a number that indicates the average value of \(X\) over numerous trials of the experiment. It is computed using the formula \(\mu=\Sigma x P(x)\). 
  • The variance \(\sigma^{2}\) and standard deviation \(\sigma\) of a discrete random variable \(X\) are numbers that indicate the variability of \(X\) over numerous trials of the experiment. They may be computed using the formula \(\sigma^{2}=\left[\Sigma x^{2} P(x)\right]-\mu^{2}\), taking the square root to obtain \(\sigma\).