Non-determinism
Ask an answer engine the identical question twice and you can get two different answers. This is the property that breaks every naive measurement in the subject.
Checkable · the test is below
What it means
These systems assemble an answer probabilistically rather than looking it up. Run the same words again and the assembly can land somewhere else. It is designed behaviour, not an error, and no vendor can switch it off for you.
Why it matters for an HVAC company
It makes a screenshot worthless as evidence. If your agency shows you ChatGPT naming your company, the honest questions are how many times they asked and how many times you appeared. One in ten and eight in ten are entirely different business situations, and the screenshot looks identical either way.
What would settle it
Test it yourself in five minutes. Open a logged-out session, ask who the best heating contractor in your town is, and ask it ten times in new conversations. Write down the names each time. The lists will differ, and you have measured it directly.
A worked example
A contractor appears in runs 2, 5, 6 and 9 of ten, so four times. A competitor appears nine times. A month later, after work on listings and reviews, the same ten runs name the contractor seven times. The direction is worth having and the cause is not established.