data presentationHistograms are a useful method of data presentation. Students often get confused between histograms and bar charts. However, histograms and bar charts are different in a number of ways. Firstly, histograms are used to present continuous data whereas bar charts are used to display discrete data. Secondly, and more importantly, histograms are not plotted against frequency, they are plotted against frequency density. This means that the frequency is represented in the area of the bar.