To choose between concepts fairly, list criteria taken from the need, score each concept against them, and weight the criteria by importance. The table does not decide for you, but it makes your reasoning open to check.
This lesson is part of the SPM subjects and learning resources section. If you have not written your need statement yet, start with define the need before the solution.
How do I build the table?
- Take three or four criteria straight from the need statement.
- Give each a weight from 1 to 3 (3 is most important).
- Score each concept from 1 to 3 on each criterion (3 is best).
- Multiply score by weight, then add the totals.
Worked example: keeping sugar ant-free
Here is an original example. The need: keep a stall’s sugar dry and ant-free overnight on one shelf, under RM20. Three concepts: A is a tin with a tight lid, B is a tray with a water ring, C is a hanging jar.
Criteria and weights: effectiveness against ants (weight 3), low cost (weight 2), easy to clean (weight 1).
| Concept | Effectiveness (×3) | Cost (×2) | Cleaning (×1) | Total |
|---|---|---|---|---|
| A: lidded tin | 2 × 3 = 6 | 3 × 2 = 6 | 3 × 1 = 3 | 15 |
| B: water-ring tray | 3 × 3 = 9 | 3 × 2 = 6 | 1 × 1 = 1 | 16 |
| C: hanging jar | 2 × 3 = 6 | 2 × 2 = 4 | 2 × 1 = 2 | 12 |
Concept B wins by one point. It is the most effective against ants, which the need puts first, even though it is harder to clean.
Does the winner depend on the weights?
Yes, and that is why you must justify them. Suppose the stall owner washes containers daily, so cleaning becomes weight 3 and effectiveness drops to weight 2.
- A: 2 × 2 + 3 × 2 + 3 × 3 = 4 + 6 + 9 = 19
- B: 3 × 2 + 3 × 2 + 1 × 3 = 6 + 6 + 3 = 15
- C: 2 × 2 + 2 × 2 + 2 × 3 = 4 + 4 + 6 = 14
Now concept A wins. The concepts are identical; only the weights changed. So an answer must say why each weight reflects the user’s situation.
The mistake that costs marks
The common slip is to write criteria and scores with no sentence of justification, or to choose weights that simply favour the concept you already liked. A short check is to ask whether a user would agree with your weights.
Check yourself
A school needs a rain cover for a bicycle rack.
Concept P scores 3 on cost, 1 on strength. Concept Q scores 2 on cost, 3 on strength. Cost has weight 2 and strength weight 3. Which concept wins, and what one sentence justifies the weights?
Answer
P: 3 × 2 + 1 × 3 = 6 + 3 = 9. Q: 2 × 2 + 3 × 3 = 4 + 9 = 13. Concept Q wins.
Justification: “Strength has the higher weight because the cover must survive strong wind and rain, while a slightly higher cost is acceptable for a structure the school will use for years.”
What to study next
After choosing a concept you test it, so continue to explain a prototype observation without overclaiming. Then try the Invention original practice set.
Use the structured answer self-review to check that each score has a reason. A teacher can work through your own table in online one-to-one Invention tuition.