diff --git a/education/statistics/random-variable.md b/education/statistics/random-variable.md index 0c09e14..b2fa5eb 100644 --- a/education/statistics/random-variable.md +++ b/education/statistics/random-variable.md @@ -2,7 +2,7 @@ title: 隨機變數 (Random Variable) description: published: true -date: 2025-12-28T17:19:02.040Z +date: 2025-12-28T17:19:30.971Z tags: editor: markdown dateCreated: 2025-12-28T16:41:51.938Z @@ -14,50 +14,46 @@ dateCreated: 2025-12-28T16:41:51.938Z A set of probability value **p~i~** assigned to each of the values taken by the discrete random variables **x~i~**. -$0 \leq p_i \leq 1$ and $\sum_{p_i} = 1$ +and -Probability -$P(X = x) = p_i$ +Probability -Expectation -$E(X) = \sum_{i} p_i x_i$ +Expectation ### Cumulative Distribution Function (CDF) -$F(X) = P(X \leq x)$ -$F(X) = \sum_{y : y \leq x} P(X = y)$ + ## Continuous ### Probability Density Function (PDF) + Probabilistic properties of a continuous random variable. -$\int f(x) \,dx\ = 1$ - -Expectation -$E(X) = \int xf(x) \,dx$ +Expectation ### Cumulative Distribution Function (CDF) -$F(X) = P(X \leq x) = \int_{-\infty}^{x} f(y) \,dy$ -$f(X) = \frac{dF(x)}{dx}$ -$P(a < x \leq b) = P(X \leq b) - P(X \leq a) = F(b) - F(a)$ -$P(a < x \leq b) = P(a \leq x \leq b)$ + + + ### Symmetric -If there is a point that, -$f(μ + x) = f(μ - x)$ -Then, -$E(X) = μ$ + +If there is a point that, + +Then, + Is the expectation of this random variable, equal to the point of symmetry. ### Median and Quantiles -The middle value of the random variable. -For median, set p to 0.5. -$F(X) = p$ + +The middle value of the random variable. +For median, set p to 0.5. ### Variance -A positive quantity that measures the spread of the distribution of the random variable about its mean value. + +A positive quantity that measures the spread of the distribution of the random variable about its mean value. Larger values of the variance indicate that the distribution is more spread out. -$Var(X) = E(X^{2}) - (E(X))^{2}$ +Missing superscript or subscript argument \ No newline at end of file