I be an HND holder and I know who I am.

They thought us that if you are erecting a building and its foundation  or structure is not good, The building would collapse one day it it even stand for you to see. If you are designing electronics, and there is a simple fault on the power supply,  your project will never work.

If you are doing any mathematical calculation, and the beginning is wrong, no matter what you do to achieve an answer ( right or wrong) at the end is wrong. This is because a wrong start at any engineering or mathematics  would bring a blown circuit board.