Lesson focus: A defensible resource decision makes values and evidence explicit, accounts for uncertaintyHow far a measurement could be from the true value, such as "25 cm, give or take 1 cm". and avoids pretending one solution fits every context.
Use a weighted decision matrix and write an evidence-based recommendation.
Build on earlier learning
Comparing energy resourcesShared comparison criteria now become a transparent decision method.
You will be successful when you can…
- Separate evidence from values.
- Apply criterion weights.
- Calculate weighted scores.
- State uncertainty and trade-offs.
Words that carry the science
- criterion
- A standard used to judge an option.
- weighting
- A number representing the relative importance of a criterion.
- trade-off
- A gain in one outcome accompanied by a cost in another.
- uncertainty
- A quantified or described limit on confidence in evidence.
- stakeholder
- A person or group affected by or able to affect a decision.
Evidence and priorities play different roles
01Evidence and priorities play different roles
Evidence estimates cost, output, emissions and impacts. weightingA number showing how important one criterion is compared with the others. express how strongly decision makers value each criterionA standard you use to judge or compare choices, such as cost or safety..
Two groups can accept the same data but reach different recommendations because their priorities differ. The weightingA number showing how important one criterion is compared with the others. should therefore be visible.
02Weighted scores support transparency
Multiply each option score by the criterion weighting, then total the products. Use consistent scales and explain what high and low mean.
A matrix organises reasoning but does not turn uncertain or incomplete evidence into certainty. Sensitivity testing checks whether a small weighting change reverses the result.
03A recommendation needs conditions
State the preferred option, cite the strongest evidence, acknowledge its main disadvantage and specify mitigation or review conditions.
stakeholderA person or group affected by a decision, such as local residents near a wind farm. evidence matters, but popularity alone does not establish scientific performance. Ethical and social judgments should be labelled as judgments.
Weight three criteria
Reliability has weight 3, emissions 3 and local impact 1. Option A scores 5, 2, 3; option B scores 3, 5, 2.
- Option A: (5×3) + (2×3) + (3×1) = 24.
- Option B: (3×3) + (5×3) + (2×1) = 26.
- B ranks slightly higher under these priorities.
- Test whether a different reliability weighting changes the ranking.
How to make the reasoning visible: The recommendation depends on both evidence scores and declared values.
Evaluate an energy proposal
Use weights reliability 3, emissions 2 and cost 1.
| Option | Reliability /5 | Emissions /5 | Cost /5 |
|---|---|---|---|
| A: gas | 5 | 1 | 4 |
| B: wind + storage | 4 | 5 | 2 |
| C: solar + storage | 3 | 5 | 3 |
| D: imported grid mix | 4 | 3 | 5 |
Calculate each weighted score.
Why should B not be recommended without qualification?
Check your understanding
Answer from memory, then check against the suggested answer.
What is a criterion?
What does a weighting show?
What is a trade-off?
A council doubles the cost weighting. Why might the ranking change?
How does sensitivity analysis improve a recommendation?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
A remote school plans to get all its electricity from solar panels.
Give two advantages of solar panels for this school.
(2)Evaluate the plan. Give two problems and a conclusion.
(4)Total for this question: 6 marks
Command word: For evaluateA command word: weigh up the good points and bad points, then give your overall judgement., use evidence on both benefits and constraints, then make a conditional judgment.