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Designers must consider the human body and human behaviour when creating products. This lesson covers ergonomics, anthropometrics and percentile data as required by AQA GCSE Design and Technology (8552), Section 3.3. These concepts are tested on Paper 2 and are fundamental to user-centred design.
Ergonomics is the study of how people interact with products, systems and environments. The goal is to design products that are comfortable, efficient and safe to use. Ergonomics considers:
| Product | Ergonomic Feature | Benefit |
|---|---|---|
| Office chair (Herman Miller Aeron) | Adjustable lumbar support, seat height, armrests, tilt | Reduces back pain during prolonged sitting |
| Kitchen knife | Contoured handle with soft-grip material | Comfortable to hold, reduces hand fatigue |
| Car dashboard | Controls within easy reach, clear instrument display | Driver can operate controls without looking away from the road |
| Games controller (Xbox) | Shaped to fit the natural grip, trigger positions match finger placement | Comfortable during extended gaming sessions |
| Computer keyboard (ergonomic split) | Split design angles the wrists naturally | Reduces risk of repetitive strain injury (RSI) |
AQA Exam Tip: Ergonomics is not just about size — it also covers comfort, ease of use and safety. The best exam answers discuss at least two of these aspects.
Anthropometrics is the study and measurement of the dimensions of the human body. Designers use anthropometric data to ensure products are the right size for their intended users.
| Measurement | Use in Design |
|---|---|
| Stature (standing height) | Door heights, ceiling clearance, shelving height |
| Sitting height | Chair back height, vehicle headroom |
| Shoulder width | Seat width, doorways, clothing |
| Arm reach (forward) | Control panel layouts, shelf depth |
| Hand grip span | Handle diameters, tool grips |
| Popliteal height (back of knee to floor) | Chair seat height |
| Buttock-popliteal length | Chair seat depth |
| Foot length | Shoe sizing, pedal spacing |
Anthropometric data is collected through large-scale surveys of populations. The data is published in reference tables (e.g. PeopleSize software, BS EN ISO 7250) and is broken down by:
A percentile indicates the percentage of a population that falls at or below a particular measurement. Percentile data allows designers to decide what range of body sizes their product should accommodate.
| Percentile | Meaning | Typical Use |
|---|---|---|
| 5th percentile | 5% of the population is this size or smaller | Designing for the smallest users (e.g. minimum reach distance) |
| 50th percentile | The median — 50% are smaller, 50% are larger | General reference point; NOT suitable for most design decisions |
| 95th percentile | 95% of the population is this size or smaller | Designing for the largest users (e.g. maximum door height, seat width) |
Most products are designed to fit the 5th to 95th percentile range, meaning they accommodate 90% of the target population. Designing for 100% of people is usually impractical and costly.
| Design Decision | Percentile Used | Reason |
|---|---|---|
| Door height | 95th percentile (male stature) | Must be tall enough for the tallest likely users |
| Emergency exit handle height | 5th percentile (female reach) | Must be reachable by the smallest likely users |
| Office chair seat height | Adjustable from 5th to 95th percentile | Must accommodate both small and large users |
| Guard rail height | 95th percentile (hip height) | Must be high enough to prevent the tallest users from falling over |
| Children's toy grip | 5th percentile (child hand size for target age) | Must be small enough for the youngest children in the age range to hold |
AQA Exam Tip: A common exam mistake is to say "design for the average (50th percentile)." This is usually WRONG. If you design a door height for the average, half the population is taller and will hit their head. Always think about which percentile matters for the specific design decision.
| Factor | Consideration | Data Source |
|---|---|---|
| Desk height | Must suit the sitting elbow height of 11–16 year olds | Anthropometric tables for children; use adjustable height or multiple sizes |
| Seat height | Must match popliteal height (back of knee to floor) so feet rest flat | 5th percentile (Year 7) to 95th percentile (Year 11) |
| Desk depth | Must allow a textbook, exercise book and pencil case | Anthropometric data for arm reach; typically 500–600 mm |
| Desk width | Must accommodate a laptop and writing space | Shoulder width data plus working area; typically 600 mm minimum |
| Edge profile | Rounded to prevent injury if a student falls against it | Ergonomic safety consideration |
| Under-desk legroom | Must accommodate 95th percentile thigh thickness | Anthropometric thigh clearance data |
Ergonomics also applies to screens, apps and digital interfaces:
Ergonomics ensures products are comfortable, efficient and safe. Anthropometrics provides the body measurement data needed to size products correctly. Percentile data allows designers to target specific ranges of the population. Together, these human factors are essential for creating products that genuinely work for the people who use them.
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