Histograms A histogram is a specialized type of bar chart. Individual data points are grouped together in classes, so that you can get an idea of how frequently data in each class occur in the data set.
High bars indicate more points in a class, and low bars indicate less points.
In the histogram show above, the peak is in the 40-49 class, where there are four points. The first is that histograms can be manipulated to show different pictures. If too few or too many bars are used, the histogram can be misleading. This is an area which requires some judgment, and perhaps some experimentation, based on the analyst's experience. Histograms can also obscure the time differences among data sets.