Example
Construct the regression line of the following data,
calculate r, a and b. Then find the unknown conc. (in
ppm) of a sample giving response 15.2 (using equation
and by interpolation)
Riboflavin (ppm)  Response
       0.05          2.2
      0.100          5.80
      0.200
      0.400         12.20
      0.800         22.30
                    43.30