imgur.com/KK2GH1T #20

I got r as .97, n=8, and c=.811 using a .005 tail, this means positive correlation. Is this correct?

imgur.com/F5OhMMr #20

I got Tophat y= -2007+7177x

then tophat y(1.5)= -2007+7177(1.5)

= price of 8,8785.5 Dollars, not close to the actual price of 16,097 dollars. Why cannot we predict the price of a 1.50 carat diamond?