Mobile-phone manufacturers would like us to believe that phone quality is closely reflected by its price, with the assumption that better quality phones are more expensive. Suppose we want to test this assertion by developing a model to predict phone price by its overall quality rating score. The scatterplot of price versus overall quality score for 21 makes and models of mobile phones currently on offer, together with the equation of a fitted regression line, is shown below.

Mobile phone price vs overall quality score 800 700 600 500 Price ($) 400 300 200 y = 51.919x - 2938.5 100 R2 = 0.3221 O 60 62 64 66 68 70 Overall quality score (%)