CEA Human Factors Engineering 3 — Questions and Answers
Question 1: A control-display ratio (C/D ratio) that is too high will most likely result in:
- Sluggish response requiring excessive control movement (Correct answer)
- Overshoot and instability during fine adjustments
- Increased cognitive load on the operator
- Reduced tactile feedback
Correct answer: Sluggish response requiring excessive control movement
A high C/D ratio means a large control movement produces a small display change, making the system feel sluggish and requiring excessive physical effort for coarse positioning.
Question 2: The 'magical number 7 ± 2' principle, attributed to George Miller, relates to limitations in:
- Sensory memory capacity
- Short-term/working memory capacity (Correct answer)
- Long-term memory retrieval
- Attention switching speed
Correct answer: Short-term/working memory capacity
Miller's 1956 paper demonstrated that short-term memory can hold approximately 7 ± 2 chunks of information simultaneously.
Question 3: Which type of human error involves executing the correct plan but performing the wrong action due to habit or inattention?
- Mistake
- Lapse
- Slip (Correct answer)
- Violation
Correct answer: Slip
A slip occurs when intentions are correct but execution fails, often due to automatic behavior overriding intentional control.
Question 4: The GOMS model in human factors is primarily used to:
- Evaluate physical fatigue in repetitive tasks
- Predict expert user performance time for cognitive tasks (Correct answer)
- Measure workload during emergency scenarios
- Classify types of human error in complex systems
Correct answer: Predict expert user performance time for cognitive tasks
GOMS (Goals, Operators, Methods, Selection rules) predicts expert task completion time by modeling the cognitive and motor steps required.
Question 5: Ecological interface design (EID) is specifically intended to help operators:
- Learn procedural tasks faster through guided tutorials
- Perceive system constraints and relationships directly from the interface (Correct answer)
- Reduce screen clutter by hiding infrequently used controls
- Standardize alarm systems across multiple plant types
Correct answer: Perceive system constraints and relationships directly from the interface
EID maps the work domain's physical and functional constraints onto the interface so operators can perceive system state without abstract interpretation.
Question 6: When evaluating a visual display, which principle states that elements close together are perceived as belonging to the same group?
- Similarity
- Continuity
- Proximity (Correct answer)
- Closure
Correct answer: Proximity
The Gestalt principle of proximity states that spatially close elements are perceptually grouped together, influencing how operators scan and interpret displays.
Question 7: In dual-task experiments, the psychological refractory period (PRP) refers to the delay in responding to a second stimulus because:
- The sensory system requires recovery time after the first stimulus
- Central processing of the first task blocks processing of the second (Correct answer)
- The motor system is still executing the response to the first task
- Attention is captured by the more salient stimulus
Correct answer: Central processing of the first task blocks processing of the second
The PRP occurs because humans have a central processing bottleneck; the cognitive response-selection stage for the second task must wait until the first is complete.
CEA Human Factors Engineering 3
A control-display ratio (C/D ratio) that is too high will most likely result in: