Using the actual dimensions of commercial steel pipe from Appendix F, plot the pipe wall thickness versus the pipe diameter for both Schedule 40 and Schedule 80 pipes, and fit the plot with a straight line by linear regression analysis. Rearrange your equation for the line in a form consistent with the given equation for the schedule number as a function of the wall thickness and diameter:

\[\text { Schedule No }=\left(1750 t_{s}-200\right) / D\]

and use the results of the regression to calculate values corresponding to the parameters 1750 and 200 in this equation. Do this using (for $D$ ) (a) the nominal pipe diameter and (b) the outside pipe diameter. Explain any discrepancies or differences in the numerical values determined from the data fit compared to those in the equation.