A district transport officer argues: 'Our learner's licence test has grown stricter. Since it was shifted to the terminal in the office, the share of candidates who fail has doubled.' Which of the following is an assumption on which the officer's argument depends?

A doubled failure share is what a harder test would produce and what an unchanged test put to weaker candidates would produce just as well, so the officer's inference holds only if the second account is shut out — that is, only if the candidates are much the same people they were. Deny it, and the whole rise is explained without the test having changed by a hair. The empanelment of the supplier bears on how the terminal was bought; the seven-day rule bears on what a failed candidate may do next; and a written record of marks bears on how the office keeps its papers. The argument runs exactly as it does whether or not any of the three is true.