https://k4i.top/tags/probability/Recent content in Probability on k4i's blogHugo -- gohugo.ioensky_io@outlook.com (K4i)sky_io@outlook.com (K4i)All content is subject to the license of <a rel="license noopener" href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank">CC BY-NC-SA 4.0</a> .Thu, 02 Jul 2026 10:00:00 +0800https://k4i.top/posts/common-distributions-variance-std/Thu, 02 Jul 2026 10:00:00 +0800sky_io@outlook.com (K4i)Thu, 02 Jul 2026 10:00:00 +0800https://k4i.top/posts/common-distributions-variance-std/<p>Probability distributions can easily turn into a formula list: Bernoulli, Binomial, Poisson, Normal, Exponential, Gamma, Beta, and so on. If we only memorize probability mass functions or density functions, the names blur together quickly.</p> <p>A more durable way to remember them is to ask two questions first:</p> <ul> <li>what is the random variable counting or measuring?</li> <li>how much does it vary around its center?</li> </ul> <p>The mean answers &ldquo;where is the center?&rdquo; Variance and standard deviation answer &ldquo;how spread out is it around that center?&rdquo; This post puts common distributions on one map, focusing on their mean, variance, standard deviation, and the intuition behind the formulas.</p>K4ifeatured imageprobabilitystatisticsdistributionvarianceMath