Diagrammatic Representation of Data — Bar Diagrams

Once data has been tabulated, it can be presented visually in two broad ways that the BIEAP Class 11 Commerce Economics syllabus takes up in turn: diagrams (geometric figures such as bars and pies, generally used for discrete or qualitative data) and graphs (figures plotted on two perpendicular axes, generally used for a continuous frequency distribution, covered in Sections 4–5). Both aim at the same purpose — making numerical facts easier to grasp and compare at a glance than a table of figures can — but a diagram trades away some precision for visual appeal, so it is best used for a quick, approximate comparison rather than for an exact reading of values.

Bar diagrams represent each value of a variable by a bar (a rectangle) of uniform width, with the length (or height) of the bar drawn proportional to the value it represents. Bars are kept at equal distances from one another, and only the length of the bar carries meaning — its width is fixed purely for visual clarity and has no numerical significance of its own.

Types of bar diagram:

• Simple bar diagram — presents a single variable across categories or time periods, e.g., a state's total revenue for five successive years, each year's revenue shown as one bar.
• Multiple bar diagram — places two or more related, separately-scaled bars side by side for each category, allowing a direct visual comparison, e.g., a state's revenue and expenditure shown as a pair of bars for each of several years. …