The hypothesis, and three sources of day-one evidence
If ten other factories are on time with the same trucks, the trucks are innocent. One comparison just pruned a branch.
A hypothesis is a proposed explanation based on early evidence - a starting point for investigation. Try to disprove it; when it dies (the trucks are top-notch) form the next one, and by crossing off issue-tree branches you may reach the answer by elimination. Orientation on day one: 1) internal benchmarks vs industry (truck age, mileage, capacity; annual-report fleet spend); 2) the trend line (did performance decline when servicing moved from six-monthly to yearly?); 3) comparison with other divisions (same trucks, on time elsewhere -> location or pre-road issue). Each source becomes a question to ask the client. 'The importance of asking good questions.'
Turns a guess into a testable claim with a plan to test it.