Elementary Statstics

5.2.4 Range chart

It is a very good method of showing the range of variation, ie. The minimum and maximum values of a variable. For example, if we are interested in showing the minimum and maximum price of a commodity for different periods of time or the minimum and maximum temperatures, or the minimum and maximum price of shares of some company for different periods, the range chart would be very appropriate. The above data can be best represented through a range chart, the following are the steps in constructing such a chart : 1. Take time on the X-axis and the variable on the Y-axis. 2. Draw two curves by plotting the given data – one curve representing the highest values and the other one the lowest values. Curve A represents lowest prices, whereas curve B highest prices. The gap between curve A and curve B represents the range of variation. 3. For emphasing difference between the lowest and higher values the use of colour or some shade, etc. should be made.