Histogram

A Histogram is a type of graphic visualization that uses vertical bars to represent tabulated frequencies. The bars which represent categories are adjacent and the area of the bar represents the value of the category, as opposed to the height of the bar in a true bar graph. The area of each bar is proportional to the frequency of the corresponding interval. When the class intervals are of equal size the height of each bar is proportional to the frequency. The shape of the graph describes how the categories are distributed about the mean and they allow the graph user to analyze large datasets on a single graph by showing the primary, secondary and tertiary peaks along with a visual representation of the peaks’ statistical significance. It is often necessary to condense the data into ranges or classes defined by intervals, as in the example above. This histogram shows the frequency distribution of the liveweights of 150 chickens selected randomly from a market.