Dotplots and histograms are both graphical displays that can be used with one quantitative variable. Below are descriptions for each along with some examples and instructions for constructing each in Minitab Express.

A dotplot can also be used to display data concerning one interval- or ratio-level variable. Each dot represents one, or more, data points. In the first example below, each dot represents one observation.

In this second example, the key at the bottom tells us that each dot may represent up to 2 observations. 

Later in the course, in Lessons 4 and 5, we will study statistical inference and the application we will use will rely heavily on dotplots. For example, we will use dotplots to determine the proportion of points greater than, less than, or between two values. This can be determined by counting the dots.

A histogram displays data concerning one interval- or ratio-level variable. On a histogram, the bars are touching, which is in contrast to the bar charts we saw earlier in this lesson with spaces between their bars.

The height of each bin (i.e., bar) communicates the number of cases with observations in that range. The histograms below both display data concerning the number of online courses completed by a sample of 324 STAT 200 students. The first histogram uses vertical bars; this is the default in most statistical software programs. The second histogram uses horizontal bars. From these plots, we can determine that the range of scores is approximately 0 to 75 online courses completed. The mode, which is the highest bar, is 0 to 5 online courses courses.