Science and public issues · Ciência e questões públicas
| English | Português |
|---|---|
| risk/rɪsk/ | risco |
| communicating uncertainty/kəˈmjuːnɪkeɪtɪŋ ʌnˈsɜːtənti/ | comunicação da incerteza |
Lower power answers only one question
- A school compares a 60 W lamp with a 10 W lamp for 5 hours daily over 20 days. Assume both draw their stated constant power during the same 100-hour operating period.
- This permits an energy estimate. It does not yet establish equal brightness, suitability, total cost or a decision to replace the lamps.
In this fictional lamp exercise, which statement is a recommendation rather than a numerical estimate?
The recommendation goes beyond a numerical estimate. Suitability, cost, values and approval must also be considered.
Calculate energy in compatible units
- Electrical energy follows $E=Pt$. Convert power to kilowatts when time is in hours: 60 W is 0.060 kW and 10 W is 0.010 kW.
- The estimates are $E_{\text{old}}=0.060\times100=6.0\ \text{kWh}$ and · e $E_{\text{new}}=0.010\times100=1.0\ \text{kWh}$. Their difference is $\Delta E=6.0-1.0=5.0\ \text{kWh}$.
Under the stated constant-power, 100-hour assumptions, what energy reduction is estimated in kWh?
E = Pt gives 6.0 and 1.0 kWh; ΔE = 5.0 kWh.
Distinguish operating savings from total cost
- If the fictional task adds a constant tariff of 0.80 RMB per kWh, the energy-cost reduction is $\Delta C=\Delta E\times r=5.0\times0.80=4.0\ \text{RMB}$ over that period.
- Without a tariff, energy alone cannot give a money saving. Even with it, purchase, installation and maintenance costs remain separate; a 4.0 RMB operating saving need not mean a lower total cost.
At the fictional constant tariff of 0.80 RMB/kWh, what energy-cost reduction follows from 5.0 kWh saved, in RMB?
ΔC = ΔE × r = 5.0 × 0.80 = 4.0 RMB; other costs are separate.
Describe the relevant risk and comparison
- Risk 风险 involves both the likelihood and seriousness of harm under stated conditions. A rare severe harm and a frequent minor harm are different patterns, not interchangeable labels.
- Name the use conditions, possible harm and relevant alternative. A broad “safe” claim needs clarification; missing evidence does not prove no risk.
Assessing a risk properly needs which of these? Choose all that apply.
Likelihood, seriousness and relevant alternatives help assess a decision. Clarify what safe means under the actual use conditions; a broad label is not automatically unanswerable.
Communicate what the estimate leaves unknown
- Communicating uncertainty 传达不确定性 includes stating assumptions and limits. Here, operating time and constant power are supplied assumptions; no measured uncertainty interval is provided.
- Report the 5.0 kWh estimate alongside what could change it, such as different hours of use or actual power. Do not invent a range or promise a conclusion will never change.
A faithful summary is: “Under the stated 100-hour, constant-power assumptions, estimated energy use falls from 6.0 to 1.0 kWh. At the fictional tariff, that saves 4.0 RMB in energy costs; lighting suitability and other costs need checking.”
Which summary faithfully reports the supplied lamp calculation and its limits?
The bounded summary preserves the estimate and missing inputs. It does not promise that a conclusion remains unchanged after future evidence.
Stating uncertainty automatically makes an otherwise identical finding weaker evidence.
Reporting uncertainty accurately helps interpret the claim. It does not by itself make every study stronger than another; compare methods, scope and actual evidence.
Use evidence to inform a decision
- A measurement can answer “How much energy is used over the same period?” Decisions also involve costs, needs and values, such as whether the intended room receives suitable lighting.
- Separate the numerical estimate from the recommendation and identify the missing evidence. Analyse the supplied record; real electrical work requires school approval and authorised personnel.
Use defined comparison → equation and units → estimate → limits → decision criteria. A lower-power label alone does not settle every criterion.
Rewrite “is this lamp the best choice?” as a specific question that can be investigated with measured evidence.
Example: “How much energy does each lamp use over the same operating period?” Other suitability and cost questions still remain.
A 4.0 RMB saving in energy costs proves a lower total cost even though purchase and installation costs are unknown.
False: those costs can outweigh the operating saving.