Seeing such a rapid increase in drive time predicted for late departures makes
Mark more aware of how much the response depends on what time he leaves home. He realizes that a 5‐minute deviation one way or the other would not be an unreasonable expectation. How will this cause the drive time to vary? Perhaps by
aiming for a specific departure time, Mark might reduce drive‐time variation caused by day‐to‐day differences when he leaves for work. Via its capability to calculate and plot propagation of error (POE), Design‐Expert can provide enlightenment on these issues.