Arithmetic mean

**Arithmetic mean:**

\begin{align} \bar X = \frac{{\sum\nolimits_{j = 1}^N {{X_j}} }}{N} \end{align}

**Weighted arithmetic mean:**

\begin{align} \bar X = \frac{{\sum\nolimits_{j = 1}^N {{w_j}{X_j}} }}{{\sum\nolimits_{j = 1}^N {{w_j}} }} \end{align}

page revision: 2, last edited: 19 Jun 2011 11:57