Definition
Diagrammatic and graphic presentation of data
Statistics • Data Classification
Statement
In a diagrammatic presentation the figures are carried by the size of a picture — the lengths of bars in a bar diagram, the angles of sectors in a pie-diagram, the number of symbols in a pictogram — and no measured scale is needed; in a graphic presentation the variable and its frequency are plotted against a pair of measured axes, as in a histogram, a frequency polygon or an ogive.
How to use it
- 1Ask whether the device needs axes: if it does not, it is a diagram.
- 2Bar diagram, pie-diagram and pictogram are the three standard diagrams; histogram, frequency polygon and ogive are the three standard graphs.
- 3A diagram compares totals between categories; a graph shows how a frequency distribution is shaped.
Worked example
Classify each as a diagram or a graph: a pie-diagram of a household budget, a pictogram of the tractors owned in four villages, an ogive of examination marks.
Step-by-step
- 1
Why: Both carry the figures by the size of a picture and need no measured axis.
- 2
Why: Cumulative frequency is plotted against the variable on measured axes.
Answer
Pie-diagram and pictogram are diagrams; the ogive is a graph.
Watch out
A histogram is bar-shaped but is a graph, not a bar diagram: its bars stand on a continuous measured scale and their areas, not their lengths, carry the frequencies. The bars of a bar diagram are separated and may be drawn in any order.
Also known as
diagrammatic presentation, presentation of data, bar diagram, pie-diagram, pictogram, diagram versus graph, types of statistical diagrams