A histogram consists in erecting a series of adjacent vertical rectangles on the sections of the horizontal axis (X-axis), with bases (sections) equal to the width of the corresponding class intervals and heights, are so taken that the areas of the rectangles are equal to the frequencies of the corresponding classes. In this article, we list out some of the merits and demerits/limitations of using histograms to represent data in statistics.
Advantages of Histogram:
- It is one of the most popular and commonly used devices for charting continuous frequency distribution. A single glance at a histogram gives us some idea about the shape and spread of the data.
- Histograms are widely used in the corporate sector in marketing campaigns and project management for the purpose of data visualisation.
- Histogram may be used for the graphic location of the value of Mode.
- The advantage of histogram over a bar chart is that both the width (base) and the length (height of the rectangle) are important and carry numerical information whereas bar diagram is one-dimensional diagram in which only length (height of the bar) matters while width is arbitrary.
- An advantage of histogram over pie charts is that a histogram can represent a large number of bars representing different class intervals. Pie charts on the other hand cannot have more than five or so “slices”/categories since too many slices look visually unappealing.
- We can use a histogram in order to draw a frequency polygon. First draw the histogram of the given frequency distribution and then join the mid-points of the tops (upper horizontal sides) of the adjacent rectangles of the histogram by straight line graph. The figure so obtained is called a frequency polygon.
Disadvantages of Histogram:
- Suppose you want to represent the sales of four different types of cars pictorially. This cannot be done using a histogram since we can only draw numerical values on the X axis when drawing a histogram. In order to deal with categories such as type of cars, we need to draw a bar graph.
- A histogram cannot be used to represent discrete frequency distributions. It can only be used to represent continuous frequency distributions.
- A disadvantage of histogram compared to a boxplot is that a boxplot gives us extra information such as the median, upper quartile and lower quartile of the data.
- Histograms cannot be used to compare two different data sets. On the other hand, multiple bar graphs can be used to compare two different data sets.
- While the mode can be calculated using a histogram, the mean and the median cannot be calculated using a histogram.
- Histograms can’t be constructed for frequency distributions with open end classes unless we assume that the magnitude of the first open class is same as that of the succeeding (second) class and the magnitude of the last open class is same as that of the preceding (i.e., last but one) class.