Chapter 1 - Linear Functions - 1.3 The Least Square Line - 1.3 Exercises - Page 33: 4

C) 0.5

We are given X: $6.8$ $7.0$ $7.1$ $7.2$ $7.4$ Y: $0.8$ $1.2$ $0.9$ $0.9$ $1.5$ $\Sigma X=35.5$ $\Sigma Y=5.3$ $\Sigma XY=37.81$ $\Sigma X^2 = 252.25$ $\Sigma Y^2 = 5.95$ $r=\frac{n(\Sigma xy)-(\Sigma x)(\Sigma y)}{\sqrt n(\Sigma x^2)-(\Sigma x)^2.\sqrt n(\Sigma y^2)-(\Sigma y)^2}$ $=\frac{5(37.81)-(35.5)(5.3)}{\sqrt 5(252.25)-(35.5)^2.\sqrt 5(5.95)-(5.3)^2}$ $=0.6985$ $r^2 = 0.5$ The correct answer is C