03 / DECIDE

Why a single number can give the wrong impression

Suppose an estimate says 118 g remain and a job needs 112 g. The six-gram difference looks reassuring. But the midpoint hides what is unknown.

The same case, with bounds

Illustrative loaded spool: 318–322 g. Tare: 198–206 g. Available mass: 112–124 g. Job: 104–110 g. Extra reserve: 5 g. Required mass: 109–115 g. Worst-case headroom: 112 − 115 = −3 g. Best-case headroom: 124 − 109 = 15 g.

Those ranges overlap. The tool reports “Uncertain,” rather than treating the midpoint as a reliable decision. This is not a probability of failure, a confidence interval, or proof that the extremes will happen together.

Three outcomes, one rule

Fits the entered ranges

The lowest available mass is at least the highest required mass. Conditional on complete, valid bounds; not a print guarantee.

Short across the entered ranges

Even the highest available mass is below the lowest required mass.

Uncertain

Some combinations fit and some do not. Equality at the optimistic edge also stays uncertain when the pessimistic edge does not fit.

What to do with an uncertain answer

Check which source has the widest plausible range. Improve that measurement or accounting, then recalculate. Do not shrink the bounds just to change the verdict. The tool helps identify an unresolved decision; it never starts or controls a printer.

Printable measurement worksheet

Print this page or use the tool’s downloadable calculation record. Keep identifiers locally; do not send client designs or personal information.

All numbers above are synthetic. No real measurements or user outcomes have been collected.

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