Inference, regression, and probability distributions.
Comprehensive descriptive and inferential statistics: Mean \(\bar{x} = \frac{1}{n}\sum x_i\), Sample Variance \(s^2 = \frac{1}{n-1}\sum (x_i - \bar{x})^2\), Standard Deviation \(s\), Standard Error \(SE = s/\sqrt{n}\). Five-number summary: Min, \(Q_1\), Median \(Q_2\), \(Q_3\), Max with Interquartile Range \(IQR = Q_3 - Q_1\). Ordinary Least Squares (OLS) Linear Regression \(y = \beta_0 + \beta_1 x\) with slope \(\beta_1 = \frac{\text{Cov}(x,y)}{\text{Var}(x)}\) and Pearson correlation coefficient \(r = \frac{\text{Cov}(x,y)}{s_x s_y}\).