HCD.9:5.2 - Turn a Pump Claim into a Discriminating Observation

Use the public pump task in HCD.6:5.1, including its 20 kW/100 m³/h baseline, measurement uncertainty, comparison model and protected observation time. The learner’s attempt uses 22.3 kW and 99.5 m³/h and concludes that increased energy per volume proves higher resistance. The calculation and supplied uncertainty bounds support the increase and weaken the measurement-error explanation; resistance and regulation efficiency remain rivals.

Feedback preserves the calculation and asks which feasible pressure observation would distinguish the leading explanations. The learner revises the claim, requests the comparable pressure observation within the remaining one and a half specialist-hours supplied by HCD.6:5.1, and states how a value near 448 kPa would support increased resistance under the stipulated model while a value near 400 kPa would redirect attention toward regulation efficiency. The correction is the conditional explanation and observation choice, not a teacher-supplied cause.

A later case changes uncertainty or omits comparable pressure data. If no obtainable measurement can improve the current explanation or response enough to justify its full preparation, specialist, comparison and displaced-work burden, the learner can finish with the supported energy-per-volume change and qualified rival explanations. A feasible present response is to return that bounded account to the responsible practitioner while leaving a resistance-specific remedy unselected. The cause remains unresolved; the useful calculation and explanation do not become incomplete merely because no new measurement is commissioned. Under the stated practice criteria, this can be a successful corrected retry.

When the changed condition instead makes the pressure observation useful enough to warrant its obtainable cost within the real window, select it and state how its possible values change the response. Keep the observation result unknown until it is obtained. Neither branch permits a unique-cause claim from the energy calculation alone; actual operating protections retain their own conditions and authority.