Validity of the regression equation.

[Tansai]

Along with this post, I have attached a screenshot of my assignment and I am confused about the validity of regressions equations. I plotted linear and exponential trend lines and got the regression equations. When I tried to verify the equations by substituting x-values in those equations, I got strange values as shown in the sheet. So, is it normal to get y-values or did I made any mistake. Any leads on this is highly appreciated. Thank you.

 

[Miner]

If you analyze the residuals, you will find that Angola is an outlier. This might indicate that there is a lurking variable that, in addition to your current x, might better explain y.