Comparing Competing Design Solutions
Aligned to MS-ETS1-2 — Next Generation Science Standards.
What this lesson teaches
When several designs could solve a problem, engineers do not just pick a favorite — they compare them fairly against the same criteria (what the solution must do) and constraints (the limits, like cost or materials). A decision matrix scores each option so the choice is based on evidence, not opinion.
Worked examples
Example 1
To choose a lunchbox that keeps food cold, you list criteria (cold for four hours, under $15, light enough to carry) and rate three boxes 1 to 5 on each. One is coldest but too heavy; another is cheap but warms fast; the third scores well on every criterion — so the matrix, not a hunch, points to the winner.
Example 2
Weight the criteria before you score. If staying cold matters three times as much as price, say so first, not after you see the results.
Example 3
A criterion you cannot measure is not a criterion. 'Looks good' cannot be scored; 'fits in a standard backpack' can.
Practice questions
- Pick a simple problem and write down two criteria and one constraint a good solution must meet.
- Make a decision matrix comparing two products you own and score each on your criteria.
- Explain why using the same criteria for every option makes the comparison fair.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Comparar soluciones de diseño rivales
Cuando varios diseños podrían resolver un problema, los ingenieros no eligen solo su favorito: los comparan de forma justa con los mismos criterios (lo que la solución debe lograr) y las mismas restricciones (los límites, como el costo o los materiales). Una matriz de decisión califica cada opción para que la elección se base en evidencia, no en opinión.
Ejemplo 1: Para elegir una lonchera que mantenga fría la comida, enumeras criterios (fría por cuatro horas, menos de $15, ligera para cargar) y calificas tres loncheras del 1 al 5 en cada uno. Una es la más fría pero muy pesada; otra es barata pero se calienta rápido; la tercera puntúa bien en todos los criterios, así que la matriz, y no una corazonada, señala a la ganadora.
Ejemplo 2: Pondera los criterios antes de calificar. Si mantenerse frío importa tres veces más que el precio, dilo antes, no después de ver los resultados.
Ejemplo 3: Un criterio que no puedes medir no es un criterio. 'Se ve bien' no se califica; 'cabe en una mochila estándar' sí.
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