9th Class Mathematics Statistics Histogram

         Histogram

It is a graphical representation of a frequency distribution in the form of rectangles with class intervals as the base and height proportional to the corresponding frequencies so that there is no gap between the two successive rectangles. This method is used for the graphical representation of continuous class intervals. It is a two dimensional figure in which both the axes are used to show the data on the graph.  

To draw a histogram, follow the steps given below:

• Mark class intervals on X - axis and frequencies on Y - axis.
• The scales for both the axes need not be the same.
• Class intervals must be exclusive. If the intervals are in inclusive form, convert them to the exclusive form.
• Draw rectangles with class intervals as bases and the corresponding frequencies as heights.  

The class limits are marked on the horizontal axis and the frequency is marked on the vertical axis. Thus a rectangle is constructed on each class interval. If the intervals are equal, then the height of each rectangle is proportional to the corresponding frequency. If the intervals are unequal, then the area of each rectangle is proportional to the corresponding frequency.  

            Comparison of Histograms and Bar Graphs