Human Factors, Ergonomics, and Safety practice questions

Answer: C) Declining detection performance over time

• AIncorrect. It's declining detection.
• BIncorrect. Performance declines.
• CCorrect. Breaks and task rotation help.
• DIncorrect. It's declining detection.

Answer: A) 4 bits

• ACorrect. log₂(32/2) = log₂ 16.
• BIncorrect. That's 2D/W without the logarithm.
• CIncorrect. That's log₂ 8.
• DIncorrect. That's log₂ 32.

Answer: B) Hand-arm vibration syndrome (vibration white finger)

Cold-triggered whitening and numbness of the fingertips in someone who has used vibrating tools for years is the classic sign of hand-arm vibration syndrome (vibration white finger).

• AIncorrect. Carpal tunnel syndrome causes numbness and tingling in the median nerve area, but it does not cause cold-triggered blanching of the fingers.
• BCorrect. NIOSH describes HAVS, also called vibration white finger or Raynaud's phenomenon of occupational origin, as causing numbness, pain and blanching of the fingers in workers who use vibrating tools.
• CIncorrect. De Quervain's is inflammation of the thumb tendons at the wrist that causes pain with gripping. It does not cause blanching or episodic numbness of the fingertips.
• DIncorrect. Trigger finger causes catching or locking of a finger when it bends. It does not cause circulatory blanching brought on by cold.

Answer: C) Bend the tool, not the wrist

• AIncorrect. Handles should fit the hand.
• BIncorrect. That causes strain.
• CCorrect. It keeps the wrist neutral.
• DIncorrect. Minimize grip force.

Answer: B) 100%

For a mixed exposure, dose = 100 × Σ(Ci/Ti). Here 2/4 + 4/8 = 1.0, so the dose is 100%, which is right at the OSHA limit.

• AIncorrect. 50% counts only one segment (2/4 or 4/8). The dose must add the fractions for both noise levels.
• BCorrect. D = 100 × (C1/T1 + C2/T2) = 100 × (2/4 + 4/8) = 100 × (0.5 + 0.5) = 100%. This is exactly the permissible limit.
• CIncorrect. 75% comes from using 8 h as the permissible time for both levels (2/8 + 4/8). At 95 dBA the permissible time is only 4 h.
• DIncorrect. 150% comes from treating all 6 h as if they were at 95 dBA (6/4). The 4 h at 90 dBA have an 8 h permissible time.

Answer: A) 4 hours

• ACorrect. Each 5-dB increase halves the allowed time from 8 hours.
• BIncorrect. That's at 90 dBA.
• CIncorrect. That's at 100 dBA.
• DIncorrect. Time halves per 5 dB.

Answer: A) Keep the red/green colors and add a distinct shape or text label to each state

Because red–green deficiency is common, critical information should never depend on red and green alone. Pairing color with a redundant cue such as shape, text or position keeps the display usable for everyone.

• ACorrect. Redundant coding with shape or text lets operators identify each state without telling the two colors apart, and color still helps everyone else.
• BIncorrect. People with red–green deficiency have trouble telling some shades of red and green apart, and more saturation does not reliably fix that. Color would still be the only cue.
• CIncorrect. A legend explains the code but doesn't help an operator who can't tell the two colors apart on the screen.
• DIncorrect. Orange and yellow-green also fall along the red–green confusion axis, so color stays the only cue and it is still hard to tell apart.

Answer: B) Noise reduction rating (NRR)

• AIncorrect. That's lighting.
• BCorrect. Field performance is often lower than the label.
• CIncorrect. That's heat stress.
• DIncorrect. That's lifting.

Answer: A) A moderate level of arousal

• ACorrect. Too little or too much arousal hurts performance.
• BIncorrect. Boredom hurts performance.
• CIncorrect. Overload hurts performance.
• DIncorrect. Arousal matters.

Answer: B) Working faster usually increases errors

• AIncorrect. They usually trade off.
• BCorrect. Designs should allow suitable pacing.
• CIncorrect. They're related.
• DIncorrect. Errors usually rise.