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Subsection A.1.1 Means and Averages

Definition A.1.1 Arithmetic Mean.

For a collection of real-valued numbers, \(x_1, x_2, \dots, x_n \in \mathbb{R}\text{,}\) the arithmetic mean \(\bar{x}\) is defined as:
\begin{equation*} \bar{x} = \frac{1}{n}\sum_{i=1}^n x_i \, . \end{equation*}

Definition A.1.2 Geometric Mean.

For a collection of non-negative real values, \(\mathbf{x}=\left(x_1, x_2, \dots, x_n \right) , \quad x_i\in\mathbb{R}^{\geq 0} \quad \forall i\in\{1,\dots , n\}\text{,}\) the geometric mean \(g(\mathbf{x})\) is defined as
\begin{equation*} g(\mathbf{x}) = \left( \prod_{i=1}^n x_i\right)^{1/n} \, . \end{equation*}

Remark A.1.3.

When all \(x_i \in \mathbf{x}\) are strictly positive, \(g(\mathbf{x})\) may equivalently be expressed in logarithmic form:
\begin{equation*} g(\mathbf{x}) = \exp\left(\frac{1}{n}\sum_{i=1}^n\ln(x_i)\right) \, . \end{equation*}