When Joe's coffee nook raised the price of a latte, Joe noticed a substantial change in his daily latte sales. A price reduction caused his sales to increase. F
From this information, you can assume the demand for lattes is elastic.
Elasticity of demand refers to to whether or not price and other factors have an effect on the quantity of something sold or not sold. This is most common when trying to evaluate what would happen when the price of an item changes.