The denominator is part of the job.
Two contracts can share a pay-item definition while having very different quantities. Setup, staging, hauling and production conditions can differ. Historical data can show the difference; it does not isolate a universal causal effect of quantity.
Start with a transparent range.
The worksheet offers an optional 0.5q–2q quantity range. For an educational quantity of 1,000 short tons, that selects observations from 500 through 2,000 short tons. This is a product setting, not a statistical standard or a rule from a transportation agency.
Watch the number of contracts.
A tighter range can remove much of a sample. Below five eligible contracts, BidFigures shows observations but no historical line estimate. Five to nine contracts carry a limited-sample label. We never widen the range silently to produce a number.
Do not convert between different dimensions.
A short ton is 2,000 pounds; a metric tonne is 1,000 kilograms. These are convertible mass units. Square yards and short tons are not directly convertible. Moving from area to mass would require a defined thickness and density; this tool does not guess them.
Document your selection
Keep the selected period, quantity range, region, definition and manual exclusions with the result. The CSV export records those choices so another reader can understand which observations contributed.
Primary reference: Caltrans quantity and search-field help ↗