\begin{definition}[Definition:Mean of Grouped Data]
Let $\mathsf C_1, \mathsf C_2, \cdots, \mathsf C_n$ be classes of data.
Let $m_i$ be the class mark of the $i$th class.
Let $f_i$ be the frequency of the $i$th class.
The '''mean of the grouped data''' for $\mathsf C_1, \mathsf C_2, \cdots, \mathsf C_n$ is defined as:
:$\ds \bar x_{\mathsf C} := \frac 1 n \sum_{i \mathop = 1}^n m_i f_i$
\end{definition}