Design in theory practice questions.

A design team records the body dimensions of a user group and also measures how quickly the same users tire while operating a hand tool. Which statement describes the relationship between anthropometrics and ergonomics?

• Anthropometrics is a subset of ergonomics, which also covers physiology and psychology
• Ergonomics is a subset of anthropometrics, which also covers reach and clearance data
• The two terms name the same field of study and can be used interchangeably here
• Anthropometrics studies fatigue, whereas ergonomics studies static body measurements

Answer: Anthropometrics is a subset of ergonomics, which also covers physiology and psychology

Anthropometrics supplies the body measurements, but ergonomics is the wider study of the whole user-product interaction, including physiological load and cognitive demand. Treating the two words as synonyms is the most common error in this subtopic.

A workshop ergonomics audit records the sound pressure level at a bench, the illuminance on the work surface and the vibration transmitted by a hand tool. What do these three readings have in common?

• They are anthropometric data describing the body size of the user
• They describe the physical conditions in which the user works
• They are psychological data describing how the user feels about the task
• They are percentile values taken from a national population survey

Answer: They describe the physical conditions in which the user works

Sound, light and vibration are environmental factors: they act on every user regardless of body size or capability, and they change comfort and performance without changing how the product fits. Body dimensions and physical capability are recorded separately, as anthropometric and physiological data.

Which statement defines the ergonomic strategy known as design for adjustability?

• A dimension is fixed at the median value of the user population
• A dimension is set to the mean of the smallest and the largest user
• A dimension is variable between two stated percentile limits
• A dimension is fixed at one extreme of the user population

Answer: A dimension is variable between two stated percentile limits

Adjustability accommodates a span of users instead of one figure, so each user sets the product rather than meeting it at a single point of the distribution. Fixing the dimension at the median, or at the mean of the two extremes, leaves users at both ends working at the wrong setting.

A designer needs the space that a seated driver sweeps out while turning to operate a control on a dashboard. Which type of anthropometric data is required?

• Static (structural) data, recorded with the body held still
• Percentile data converted from a single stature measurement
• Psychological data describing how the driver perceives the space
• Dynamic (functional) data, recorded while the body is in motion

Answer: Dynamic (functional) data, recorded while the body is in motion

Dynamic anthropometrics records dimensions during movement, so it captures the true working envelope; static data taken in one fixed posture underestimates the space actually swept by the limb.

Passengers at a ticket machine hesitate because they cannot tell which button to press first. Which category of human factors does this problem belong to?

• Physiological factors, because the difficulty lies in muscular effort
• Psychological factors, because the difficulty lies in interpreting information
• Anthropometric factors, because the buttons lie outside the seated reach envelope
• Environmental factors, because ambient noise at the machine slows the user

Answer: Psychological factors, because the difficulty lies in interpreting information

Hesitation is a cognitive load problem covering perception, memory and decision-making, so it belongs to the psychological strand of human factors rather than to body size or muscular capability.

An anthropometric table gives the 95th percentile shoulder breadth of a user group as 510 mm. What does this figure mean?

• 95 % of the group have a shoulder breadth of 510 mm or more
• Shoulder breadth in the group varies by up to 95 % around 510 mm
• 95 % of the group have a shoulder breadth of 510 mm or less
• 510 mm is 95 % of the largest shoulder breadth in the group

Answer: 95 % of the group have a shoulder breadth of 510 mm or less

A percentile states a cumulative position in the distribution, so the 95th percentile value is the one that 95 % of the population fall at or below. That is exactly why clearance dimensions are taken from it.