====== Common probability distributions ====== ===== Gaussian/Normal ===== * Continuous * Parameters * $\mu \in \mathbb{R}$ (mean) * $\sigma^2 > 0$ (variance) * Support: $x \in \mathbb{R}$ * PDF: $\frac{1}{\sigma \sqrt{2\pi}}e^{-\frac{1}{2}(\frac{x-\mu}{\sigma})^2}$ * Mean/expectation: $\mu$ * Variance: $\sigma^2$ ==== Calculating CDF ==== $P(X < x)$ for $X \sim \mathcal{N}(mu, sigma)$ p = normcdf(x, mu, sigma) ====Calculating inverse CDF or quantile==== $\mathbb{P}(X \leq q) = 1 - alpha$ for $X \sim \mathcal{N}(mu, sigma)$ q = norminv(1 - alpha, mu, sigma) ===== Binomial distribution ===== * Discrete * Parameters * $n \in \mathbb{N}_0$ (number of trials) * $p \in [0, 1]$ (probability of success of single trial) * Support: $\{0, 1, ..., n\}$ * PMF: ${n \choose k} p^k (1-p)^{n-k}$ * Mean: $np$ * Variance: $np(p-1)$ ===== Bernoulli ===== * Discrete * Special case of binomial for $n=1$ * Parameter: $p \in [0, 1]$ (probability of success) * Support: $\{0, 1\}$ (either 0 or 1) * PMF: $p^k(1-p)^{1-k}$ * Mean/expectation: $p$ * Variance: $p(1-p)$ ===== Poisson ===== * Discrete * Parameter: $\lambda > 0$ * Support: $\mathbb{N}_0$ (0, 1, ...) * PMF: $\frac{\lambda^ke^{-\lambda}}{k!}$ * Mean/expectation: $\lambda$ * Variance: $\lambda$ ===== Exponential ===== * Continuous * Parameter: $\lambda > 0$ (rate) * Support: $[0, \infty]$ * Mean: $\frac{1}{\lambda}$ * Variance: $\frac{1}{\lambda^2}$