Finance: an example.
Underwriting an acquisition by hand means one model at a time, from whatever financials the current owner kept. In this example, the assistant builds the model from those financials, reads the books whichever way an owner writes them, and checks its own work before it shows a number.
An illustrative example, not a client result.
What changes.
Analysis no longer starts from a blank spreadsheet. Every computed figure is checked against the company's own model before it is shown, and every assumption is written down and can be asked about later.