Daesoo Lee's Blog

Note-taking/Books

• Head First Statistics

  Note-taking/Books 2021. 1. 16. 11:25

  Frequency Density = Frequency / Group width Cumulative Frequency Mean $$\mu = \frac{\sum_{i=1} x_i }{ n }$$ $$\mu = \frac{\sum_{i=1} f_i, x_i }{ \sum_{i=1} f_i }$$ where $f_i$ denotes frequency of $x_i$ (e.g. $x_i$ can denote a certain age, and $f_i$ is #people belonging to that age). Skewed Data When outliers pull the mean of the data to the left or right: Average There are several kinds of..

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• Practical Statistics for Data Scientists

  Note-taking/Books 2021. 1. 14. 17:17

  Ordinal: Categorical data that has an explicit ordering Records: A row in the table (dataset) Rectangular data: Data in a table form Non-Rectangular data structure: 1) Spatial data (it stores data indexed in some way by their spatial location), 2) Graph data structure Trimmed mean: It's a compromise between median and mean. The front and back ends are dropped (trimmed) by $n%$ (usually, $10%$) a..

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• An Introduction to Statistical Learning with Applications in R

  Note-taking/Books 2021. 1. 12. 17:04

  Notation and Simple Matrix Algebra $n$ to represent the number of distinct data points. $p$ denotes the number of variables. $\boldsymbol{X}$ denotes a $n \times p$ matrix whose $(i, j)$-th element is $x_{ij}$. That is, $$ \boldsymbol{X} = \begin{bmatrix} x_{11} & x_{12} & \cdots & x_{1p} \\ x_{21} & x_{22} & \cdots & x_{2p} \\ \vdots & \vdots & \ddots & \vdots \\ x_{n1} & x_{n2} & \cdots & x_{n..

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