A dot plot, also known as line plot, is a way to represent numerical data in which each data point is represented with a dot above a horizontal number line. The dots representing the same measurements are stacked above each other. Consider the following data set.

• There are two $1$s in this data set, so on the corresponding dot plot two dots are stacked above the number $1$ of the number line.
• There is one $3$ in this data set, so on the corresponding dot plot a single dot is drawn above the number $3$ of the number line.
• There are five $4$s in this data set, so on the corresponding dot plot five dots are stacked above the number $4$ of the number line.

Dot plots are normally used for discrete data. For data sets containing more than $20$ data points, dot plots are often inconvenient and other representations are preferred.