Using area to interpret a histogram's shape
For all histograms, whether drawn with equal class widths or mixed classes, the area above any class is the proportion of values in that class. This is the most important property of a histogram and should be used to help you understand the distribution of values.
For example, if half the area of a histogram is to the right of a particular value, then half of the data are above that value.
Skew data
The histogram below shows 100 values from a skew distribution using classes of mixed widths.
Drag over the two classes that cover the range of values from 2 to 6. The area is 47% of the total histogram, so 47% of the values are between 2 and 6.