Customer satisfaction is a crucial key to customer retention that firms should usually measure the pleasure of customer. According to Kotler (2009) a highly satisfied customer mainly stays loyal longer and purchases more as the firm present new products or services and upgrades existing ones. Furthermore, a person's emotions of pleasure or displeasure effect from comparing a product's perceived outcome (or performance) relation to the customer prospects involve with satisfaction.
Kotler (2000) also expresses that satisfaction is a person’s feelings of pleasure or disappointment resulting from comparing a product’s perceived performance (or outcome), in relation to his or her expectations.