Answer
The mean grip strength, $y ̅=57.0~psi$
Work Step by Step
Do not use the least-squares regression equation from part (a) because, according to item (b), we could not conclude that a linear relation exists between age and grip strength.
$y ̅=\frac{65+60+58+60+46+66+56+75+46+45+58+70+73+45+60+56+30}{17}=57.0$
