Design Loop Dynamics

Assessment Coaching Tip: Criteria vs. Constraints Confusion

Students frequently confuse criteria and constraints because both are "rules" given at the start of a challenge. Teach students the "Goal vs. Wall" Test: If it describes what the machine is supposed to do (a goal to reach), it is a Criterion. If it tells the builder what they cannot exceed or cannot use (a wall holding them in), it is a Constraint.

Engineering Design Process Study Guide © Teacher Answer Key PAGE 1 OF 2 // OBJECTIVE KEY

Constructed Response & Analysis

Diagnostic Rubrics & Distractor Analysis

Remaining Points Part 3: 8 Pts | Part 4: 6 Pts

C Part 3: Scenario Analysis & Failure Iteration Rubric (8 Points)

4 PTS PER QUESTION

Question 1: Quantitative Data & Criteria Evaluation (4 Pts) EXEMPLARY RESPONSE

Model Answer: "The quantitative data collected includes: filtering time of 2 minutes 15 seconds, light transmittance clarity of 52%, and cost of $6.50. Prototype Alpha did not meet all criteria: while it met the time criterion (< 4 min) and satisfied the budget constraint (≤ $10), it failed the critical clarity criterion by reaching only 52% instead of the required ≥ 85%."

+1 pt: Lists numerical time (2:15).

+1 pt: Lists clarity (52%).

+1 pt: States criteria was NOT met.

+1 pt: Explains comparison to 85% goal.

Question 2: Iteration Plan & EDP Stage Return (4 Pts) EXEMPLARY RESPONSE

Model Answer: "For Prototype Beta, the team should add a finer filtration layer (such as fine sand, activated charcoal, or coffee filter mesh) underneath or above the gravel to capture fine silt particles. They are returning to Step 3 (Plan & Design) to redesign the filtration medium, and Step 4 (Create & Prototype) to rebuild and retest, spending within their remaining $3.50 budget."

+1 pt: Identifies silt as the flaw.

+1 pt: Proposes finer layer/medium.

+1 pt: Identifies EDP Stage (Plan/Design/Build).

+1 pt: Acknowledges budget constraint ($3.50 left).

D Part 4: Multiple-Choice Rationales & Distractor Analysis (6 Points)

3 PTS EACH

1. Why EDP is a Cycle CORRECT: B

✓ B: Test results and failure data provide insight to redesign and refine solutions.

Distractor A: False; engineers pinpoint specific sub-assemblies rather than always restarting from step one.

Distractor C: Arbitrary; number of prototypes depends on constraints and safety standards.

Distractor D: Inverted sequence; brainstorming occurs before prototyping.

2. Iterative Prototype Improvement CORRECT: C

✓ C: Adjust only the grip material or claw friction, then re-test to evaluate improvement.

Distractor A: Changing multiple variables at once makes it impossible to isolate which change improved performance.

Distractor B: Abandoning the prototype prematurely circumvents the iterative cycle and ignores test data.

Distractor D: In engineering, failure is informative feedback that directly guides the next round of prototyping.

Top 3 Student Misconceptions to Address During Review

1. "Failure is Negative" Emphasize that an unpredicted test failure is the most valuable event in engineering—it reveals exact mechanical limits without guessing.

2. "Prototypes are Final" Remind students that a prototype is a temporary experimental tool built specifically to be tested and modified, not a commercial product.

3. "One Correct Answer" Science seeks natural truth; engineering develops optimized solutions with varying balances among cost, strength, and time.

Engineering Design Process Study Guide © Teacher Answer Key PAGE 2 OF 2 // DIAGNOSTIC RUBRIC