Any information collected can be first arranged in a frequency distribution table, and this information can be put as a visual representation in the form of pictographs or bar graphs. Graphs are a visual representation of organised data.
A bar graph is the representation of data using rectangular bars of uniform width, and with their lengths depending on the frequency and the scale chosen. The bars can be plotted vertically or horizontally. You can look at a bar graph and make deductions about the data.
Bar graphs are used for plotting discrete or discontinuous data, i.e. data that has discrete values and is not continuous. Some examples of discontinuous data are 'shoe size' and 'eye colour', for which you can use a bar chart. On the other hand, examples of continuous data include 'height' and 'weight'. A bar graph is very useful if you are trying to record certain information, whether the data is continuous or not.
Graphs can also be used for comparative analysis.
Double bar graphs are used for comparing data between two different things. The difference between a bar graph and a double bar graph is that a bar graph displays one set of data, and a double bar graph compares two different sets of information or data.