When you are investigating for the market of wheat and the price of corn which is the substitute of wheat price decreases then the demand of the wheat will decreases.
And if the demand for the wheat decrease this will lead to an increase in the surplus of the wheat and when surplus increases the price of wheat automatically goes down.
The range is the simplest measure of variation to find. It is simply the highest value minus the lowest value. Since the range only uses the largest and smallest values, it is greatly affected by extreme values, that is - it is not resistant to change
