Vendor Memo: Pitch, Trials, and the 4 km Requirement
The programme office is choosing between Vendor A and Vendor B for a shipborne electro-optical sensor. A two-page memo recommends Vendor A and states: 'Vendor A's detector pitch is 12 µm versus Vendor B's 15 µm, so Vendor A delivers 25% more detection range. In a desert trial, Vendor A detected a small boat at 4.2 km and Vendor B at 3.6 km. Vendor A costs 18% more, but it is the only bid that meets the 4 km requirement.' The requirement is 4 km in tropical maritime conditions. The trial was run at 38 °C in dry air with visibility 20 km. Vendor B's bid includes a cooled detector and a two-year calibration contract; Vendor A's does not. The memo does not mention sea state, humidity, or target contrast. The review board must decide whether the memo's conclusion is adequately supported, what the memo assumes, and what evidence would most weaken it.
1. Identify the central unstated assumption in the memo's argument and explain why it matters.
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The memo assumes that detector pitch is the dominant determinant of detection range, and that a desert trial transfers directly to tropical maritime conditions. The 25% figure appears to come from the pitch ratio 15/12 = 1.25, but no physical law makes range scale linearly with pitch. Range also depends on aperture, detector sensitivity, noise, atmospheric transmission, target contrast, and image processing. The assumption matters because the requirement is 4 km in humid maritime air, where attenuation and background clutter differ from a dry desert trial. If the assumption fails, the trial comparison does not establish that Vendor A meets the requirement. A defensible recommendation would require either maritime trial data or a modelled link budget showing margin under the specified conditions.
2. Which single piece of additional evidence would most weaken the recommendation? (a) Vendor B's unit cost is 18% lower; (b) Vendor A's detector requires a 30-minute cool-down; (c) in humid maritime air, Vendor A's range fell to 3.4 km while Vendor B's held at 3.9 km; (d) the memo was written by Vendor A's sales team.
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Option (c) is the strongest weakening evidence because it directly attacks the decisive claim: that Vendor A is the only bid meeting 4 km in the required environment. It substitutes condition-relevant performance for a desert trial and a pitch inference. Option (a) concerns cost, not operational effectiveness, and the memo already concedes the 18% premium. Option (b) is a usability drawback but does not by itself breach the range requirement. Option (d) raises a bias concern, but the board should evaluate evidence rather than motive; a sales-authored memo can still contain valid data. Only (c) shows that Vendor A may fail the actual requirement while Vendor B may meet it.
3. Distinguish the factual claims from the inferences in the memo.
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Factual claims are the stated measurements and commercial terms: 12 µm versus 15 µm pitch; detected at 4.2 km versus 3.6 km in the desert trial; Vendor A costs 18% more; Vendor B includes a cooled detector and a two-year calibration contract. Inferences are 'Vendor A delivers 25% more detection range' and 'Vendor A is the only bid that meets the 4 km requirement.' The first inference treats a pitch ratio as a range ratio, which is an engineering claim requiring justification. The second generalises from one trial in non-representative conditions to the contractual requirement. A good review separates these: the facts may be true while the inferences remain unproven. The board should request the missing maritime data or a validated performance model before accepting the conclusion.