To find the y-intercept, calculate and , the average of the x- and y-values respectively.
Then substitute these two values for x and y in the = b + a
equation. Finally, solve for the unknown quantity a. Remember from the previous page that:
Therefore, the complete relationship between glucose concentration and absorbance for the data is y = 0+ 0.002x, or y = 0.002x, where y is the absorbance and x is the glucose concentration.