I've been checking a great many documents and calculations this week as part of ensuring quality and accuracy in my latest expert witness report.
This kind of checking is an important part of engineering practice, which many engineers, (especially beginners) do not see the value of, and consequently try to avoid. However, if you do enough checking of this type, you realise that the best of us make mistakes.
The point is not to avoid mistakes in calculations or arguments, but to eliminate them to the maximum extent possible by checking and correction before they are acted on.
I do not however find that a large percentage of my expert witness work hinges on poor mathematics. Even a green engineering graduate can do a sum. The problem is very often failing to choose the person who knows which sum to do to design something.
It seems that all too often, design is carried out by people who lack the proper professional judgement, and those who are supposed to be checking their work do not take enough care in checking before appending their signature.
If that is you, try to remember that someone like me might be reading those documents you put in your outbox signed off but fundamentally unchecked twenty years later.