ECO knowledge

You can only say that the quantity demanded/ supplied along a demand/ supply curve is affected by the change in price alone. The purpose of demand curve or schedule is to show the effect of price change on quantity demanded, holding other things constant. Therefore along a demand or supply schedule, quantity is affected by price only.

An increase in income, for example, will increase quantity demanded at every price level. In other words, upward change of income increases general demand as a whole. All other factors (some more important than others), except price, will affect demand and supply (by which we mean the schedule).