Option E: Human factors design
“Human factors” and “ergonomics” are interchangeable terms—the term “human factors” is more commonly used in some parts of the world, such as the United States (US), and the term “ergonomics” is more widely used in other countries. Human factors analyses the interactions between humans and other elements in a system, and then applies principles, information and data to a design to maximize human well-being and system performance. Human factors design ensures that products, organizations, environments and systems are compatible with the needs and limitations of people. This can help to reduce the stress on people, as they will be able to do things faster, more easily, more safely and make fewer mistakes. This option builds upon knowledge gained from studying sub-topic 6.1, “Ergonomics”.
E1 Human factors design
Identify the objectives of human factors design.
Consider effectiveness (completeness and accuracy), efficiency (speed and effort), engagement (pleasantness and satisfaction), error tolerance (error prevention and error recovery) and learnability (predictability and consistency) with which activities can be carried out and how human values, for example, quality of life, improved safety, reduced fatigue and stress, increased comfort levels and job satisfaction, are enhanced.
Describe why visibility is an important consideration in human factors design.
Controls should be visible and it should be obvious how they work. They should convey the correct message, for example, with doors that need to be pushed, the designer must provide signals that indicate where to push.
Describe why feedback is an important consideration in human factors design.
Feedback is the provision of information, for example, an audible tone to a user, as a result of an action. The tone on a telephone touchpad or the click of a key on a computer keyboard provides feedback to indicate that a key has been pressed. The “egg timer” icon on a computer screen tells the user that an action is being undertaken.
Describe why mapping is an important consideration in human factors design.
Mapping relates to the correspondence between the layout of the controls and their required action. For example, the layout of the controls on a cooker hob can take advantage of physical analogies and cultural standards to facilitate a user’s understanding of how it works.
Describe why affordance is an important consideration in human factors design.
Affordance is the property of an object that indicates how it can be used. Buttons afford pushing, and knobs afford turning. On a door, handles afford pulling, whereas push plates afford pushing. Consider how the use of a handle on a door that needs to be pushed open can confuse users, and how in an emergency this might impact on safety considerations.
Describe why constraints are an important consideration in human factors design.
Constraints limit the way that a product can be used. The design of a three-pin plug or a USB (universal serial bus) device ensures that they are inserted the correct way. This reduces or eliminates the possibility of a user making errors.
Explain why consumers misuse many products due to inappropriate human factors considerations in their design.
It is not always obvious from looking at products how they should be used. Consider visibility, feedback, mapping, affordance and constraints.
Explain why the aims of human factors may conflict with other design aims.
Examine the notion of optimum compromise and consider cost, form, function, which may be more important aims to achieve in a specific design context.
Explain that the ergonomic data required in systems design depends on the role of people in that system.
Consider an operator of a system or a user of a system. Reduced system efficiency and failures that occur early in the life cycle are frequently caused by poor human factors design.
E2 Human factors data
Define user population.
Outline how large user groups may be defined.
Consider age, gender and physical condition.
Outline the importance of sampling to gain information about potential users.
When considering a product designed for mass use, it is not good to rely on information collected from just a few people, as it is unlikely to be representative of the whole range of users.
Describe how a user group sample is based on the factors considered in E.2.2.
Discuss how the factors in E.2.2 are further defined to determine the exact nature of a user group sample.
The factors in E.2.2 are all characteristics that are important to the evaluation. These characteristics are the ones that must be represented by the members of the sample.
Outline the use of the concept of “methods of extremes” to limit sample sizes.
Sample users are selected to represent the extremes of the user population plus one or two intermediate values, for example, evaluating a kitchen layout may use the shortest (2.5th percentile), the mean (50th percentile) and the tallest (97.5th percentile).
Define population stereotypes.
Describe the relevance of the use of population stereotypes in the design of controls for products.
It is usually anticlockwise for “on” when dealing with fluids and gases, for example, a tap, and clockwise for “on” when dealing with mechanical products, for example, a radio.
Discuss the problems of displacing population stereotypes in the design of controls for products.
Population stereotypes can be displaced by alternative learnt responses, but they frequently reassert themselves under conditions of stress such as tiredness or panic.
Discuss how the use of converging technology in product design may lead to confusing control layout.
For example, gas cooker controls are turned clockwise for “off”, but for an electric cooker they are the other way round. This is because the gas cooker knobs are effectively taps, operating a fluid or gas. This can be confusing for consumers and can be a safety hazard, especially with a gas hob and electric oven combined into one product.
Discuss how the concepts of “range of sizes” and “adjustability” affect the design of products.
Consider clothing, cars, furniture and the ironing board.
Compare the collection of static anthropometric data with the collection of dynamic anthropometric data.
Static data is much easier to gather, as people are asked to remain still while measurements are taken. Dynamic data involves people carrying out tasks. People carry out tasks in many different ways. While static data is more reliable, dynamic data is often more useful.
Describe the instruments used in the collection of anthropometric data.
For example, sliding calliper, stadiometer, sitting height table, cloth tapes, torso callipers, and Harpenden anthropometer.
Explain why it is difficult to obtain accurate anthropometric data using the equipment described in E.2.13.
Refer to obtaining data from nude and clothed people.
Identify an appropriate percentile range for the design of adjustable equipment.
Equipment might include car seats, office chairs, desk heights, footrests. The range from 5th percentile female to 95th percentile male will accommodate 95% of a male and female population because of the overlap between female and male body dimensions for each dimension.
Multivariate accommodation (fitting in several variables, for example, in a car you need to fit in terms of sitting height, leg room, arm reach, viewing angles, hip breadth, thigh length) means that accepting 5% being designed out for each important dimension is not viable, because different people will be designed out for each variable. People have different proportions. Those designed out because they are too tall may not be the same as those designed out because their arm reach is too short.
Explain how designers use primary and secondary anthropometric data in solving a design problem.
Discuss the importance of biomechanics to the design of a given artifact.
Consider muscle strength, age, handle size, surface texture, and torque (for example, in a can opener, valve wheel, corkscrew, door handle, jam jar lid).
E3 Research and testing
List four types of data scales.
List nominal, ordinal, interval and ratio data scales.
Describe nominal scale.
This scale only classifies objects into discrete categories, for example, food groups. Nominal means ”by name” and labels are used for the categories of objects. Nominal scales are very weak, as they do not tell you anything more than that one object is different from another.
Describe ordinal scale.
As with nominal scales, the labels used in ordinal scales can be words, symbols, letters or numerals. When numerals are used, they only indicate sequence or order, for example, ranking someone by placing them in a competition as “third” rather than by a score—they may have come third with 50% right or with 75%.
Describe interval scale.
An interval scale is a more powerful scale, as the intervals or difference between the points or units are of an equal size, for example, in a temperature scale. Measurements using an interval scale can be subjected to numerical or quantitative analysis.
Describe a ratio scale.
The difference between a ratio scale and an interval scale is that the zero point on an interval scale is some arbitrarily agreed value, whereas on a ratio scale it is a true zero. For example, 0°C has been defined arbitrarily as the freezing temperature of water, whereas 0 grams is a true zero, that is, no mass.
Explain the relevance of using the different rating scales to design contexts.
For example, a comfort rating scale of 1–10 is an ordinal scale.
Describe the human information-processing system.
For example, a car driver processes information from the road and the car, and produces various control responses such as braking or changing gear.
Explain that the human information-processing system can be represented by an information flow diagram.
The arrows represent the flow of information through the system. The boxes represent functional elements in the processing chain, where information is processed.
Apply the information flow diagram to particular contexts.
For example, when using a mobile phone to make a telephone call. The input would be the number to be called. The sensory processes would be the eyes, which would transmit information to the brain. The brain is the central processing unit, which examines the information and selects a response coded as a series of nerve impulses transmitted to the hand and muscles. These are the motor processes, which reconvert the instructions into actions, that is, outputs.
Outline how the flow process described in E.3.9 may break down.
The information inputs may be incompatible with the sensory receptors. At the central processing stage, the incoming information may be incorrect or no suitable responses to it are available. The motor output stage may be unable to perform the actions specified by the central processing unit.
Outline how motor outputs may be inhibited if the physical fit between the person and the environment is wrong.
Consider problems encountered by young children and elderly, infirm or disabled people.
Define manikin, ergonome, appearance prototype and functional prototype.
Outline the use of manikins to represent human factors data.
Manikins are used with 2D drawings, mainly orthographic drawings.
Discuss advantages and disadvantages of the use of manikins to represent human factors data.
Manikins only give an approximate idea of the relationship between sizes of body parts and sizes of objects, for example, reach. However, they are cheap and easy to use.
Outline the use of ergonomes to represent human factors data.
Ergonomes are useful for assessing the relationship of body parts to spatial arrangements represented by a 3D model, for example, a chair to a desk.
Discuss advantages and disadvantages of the use of ergonomes to represent human factors data.
Ergonomes are more expensive and time-consuming than manikins because of the need for 3D models but are more realistic representations of a design context.
Outline the use of appearance prototypes to gain human factors data.
Appearance prototypes look like but do not work like the final product. Appearance prototypes can be relatively simple, consisting of solid chunks of foam finished and painted to look like the real thing, or they can be more sophisticated, simulating weight, balance and material properties. Usually, appearance prototypes are “for show” and are not designed to be handled excessively.
Outline the use of appearance prototypes at the design development stage.
They give non-designers a good representation of what the object will look like and feel like. For example, marketing directors can make judgments and production engineers can take data for assessing feasibility for matching manufacturing systems. They are expensive to produce, as they need to have a good surface finish and be life-size.
Outline the use of a functional prototype model to evaluate human factors aspects of a design.
It allows for more interaction with potential users, for example, a range of percentile groups. Also bodily tolerances can be measured.
Discuss the advantages of the use of functional prototypes for gaining human factors data.
Identify design contexts in which clay, card and polymorph may be used for human factors modelling.
Polymorph is a new generation of non-hazardous, biodegradable polymer, which can be used repeatedly for modelling. It is supplied as granules, which are poured into hot water to make a soft, pliable material. On removal from the water, the material can be moulded into the desired shape. On cooling, it becomes a tough machinable engineering material.
E5 Health and safety legislation
Describe the objectives of product safety testing.
The objectives of product safety testing are to reduce accidents and improve the safety and physical well-being of people through:
• verification that a product is safe for intended and unintended uses
• verification that a product meets or exceeds the requirements of all safety regulations
• identification of any unforeseen ways that the product may be misused.
Identify the general human factors contributing to accidents.
Categories of factors that cause accidents include management (policies, safety education, decision centralization), physical environment (noise, temperature, pollutants, trip hazards, signage), equipment design (controls, visibility, hazards, warnings, guards), the work itself (boredom and repetitiveness, mental and physical workload, musculoskeletal impacts such as force, pressure and repetition), social and psychological environment (group norms, morale), and the worker (ability, alertness, age, fatigue).
Outline the factors that contribute to thermal comfort in office and other working environments.
Thermal comfort describes a person’s psychological state of mind and involves a range of environmental factors: air temperature, the heat radiating from the Sun, fires and other heat sources, air velocity (still air makes people feel stuffy, moving air increases heat loss), humidity, and personal factors (clothing and metabolic rate). Hopefully in an office environment where a number of people work together, the thermal environment satisfies the majority of the people. Thermal comfort is not measured by air temperature, but by the number of people complaining of thermal discomfort. Thermal comfort affects morale and productivity.
Discuss the legislative requirements for temperature in the workplace.
Legislation sets minimum and maximum temperatures for different types of workplace, and workers have the right to refuse to work if such temperatures are not maintained.
Outline the legislative requirements for decibel levels for working with machinery.
Excessive noise in the workplace can cause workers to lose their hearing and/or to suffer from tinnitus (permanent ringing in the ears). The level at which employers must provide hearing protection and hearing protection zones in, for example, the UK is now 85 decibels (daily or weekly average exposure), and the level at which employers must assess the risk to workers’ health and provide them with information and training is now 80 decibels. There is also an exposure limit value of 87 decibels, taking account of any reduction in exposure provided by hearing protection, above which workers must not be exposed.
Discuss the legislative incentives to incorporate human factors into product design.
Consider safety standards and regulations that must be followed, but also methods of avoiding future litigation against failed products. Such methods include:
• always include a “duty to warn”
• design safety into the product
• incorporate a greater safety factor than that required by legislation
• analyse all consequences of product use and misuse
• rigorously test one or more prototypes in a realistic context before finalizing the design.
Describe the methods used for identifying hazards and evaluating risks.
Methods include the following.
Scenario analysis attempts to identify patterns of behaviour that precede accidents. If such behaviour can be identified, then it may be avoided by a redesign of a product.
Fault tree analysis determines the causes of failures by first identifying the types of injuries that may occur and concluding with redesign solutions.
Hazard assessment determines probable causes for injury and indicates ways to eliminate the hazards.
Explain how human factors specialists determine adequate product safety.
Behavioural testing: perform some activity with the product such as unpacking, assembly, operation and maintenance.
Conceptual testing: evaluate safety instructions and warning messages without exposing people to hazardous conditions.
E6 Design for usability
Identify three characteristics of good user–product interfaces.
The user–product interfaces of many electronic products are extremely complex rather than being intuitive and easy to use. Products with intuitive and easily accessible interfaces are likely to be more popular with consumers (especially more affluent and older consumers). Three important characteristics are: simplicity and ease of use; intuitive logic and organization; and low memory burden. Consider which product features are essential or likely to be used with greatest frequency; the functionality required by a typical user; and the common learning problems encountered by users.
Explain the disadvantages of user–product interfaces that are not well organized and cannot be learnt intuitively and remembered easily.
Novice users of a product should be able to learn all its basic functions within one or two hours. However, many products are full of confusing detail and are difficult to learn. This can lead to incomplete use of the product’s functionality and frustration for the user. Instruction manuals are often poorly written and poorly organized.
Discuss the impact of memory burden on the user-friendliness of a product.
Poor organization of a product imposes a memory burden on users, who have to learn and remember how the various functions work. This results in them not using the full functionality of a product but focusing on a limited set of features and ignoring those that are difficult to remember. Thinking about how intuitively the product features can be accessed by users can reduce memory burden and make the product more user-friendly.
Explain why it is difficult for designers to develop simple intuitive user–product interfaces.
It is difficult for the designer of a product to distance him/herself from the product and look at it through the eyes of the prospective user. Reinnovation of a product often involves adding features to the basic design rather than redesigning the user–product interface from scratch, and this can result in a disorganized interface. It is important to consider necessary and desirable features, not ones that increase complexity without enhancing usefulness for most users.
Define paper prototyping.
Explain that paper prototyping is one example of participatory design.
Paper prototyping is sometimes called low-fidelity prototyping. It is one example of participatory design, that is, it involves users in design development.
Explain the roles of the facilitator, the user, the computer and the observer in a paper prototyping session.
Facilitator: explains the purpose of the session to the user and how to interact with the prototype.
User: represents the target market for the product, and interacts with the user–product interface to “use” the product in response to guidance from the facilitator.
Computer: a human being simulating the behaviour of the computer program in response to instructions from the user.
Observer: watches what happens and can ask more questions of the user.
Explain the advantages of paper prototyping.
It is cheap and easy to implement. A paper prototype can be quickly and easily modified and retested in the light of feedback from representative users, so designs can be developed more quickly. It promotes communication between members of the development team. No computer programming is required, so paper prototyping is platform-independent and does not require technical skills. A multidisciplinary design team can collaborate on design development.
Product: mobile phone (3 hours)
Outline three elements of anthropometric data used in the design of a mobile phone.
For example, finger dimensions, hand size, thumb width, viewing angle.
Outline one design factor related to ease of use of the mobile phone that has compromised the use of human factors data.
For example, miniaturization of components and portability.
Outline psychological human factors data that could be used in the design of a mobile phone.
For example, texture, sound, colour and light.
Discuss the relationship between fashion and human factors in the design of the mobile phone.
Fashion relates to style, for example, chunky or ultra-slim, and texture, which then have an impact on ease of use, portability.
Define aesthetic-usability effect.
Discuss how the aesthetics of a mobile phone make it look easier to use and increase the probability of it being used, whether or not it is actually easier to use.
Consider point-of-sale impact and recommendations of other users even though they have different human factors requirements.
System: kitchen (3 hours)
Describe the concept of a work triangle in relation to kitchen layout.
A work triangle is used to assess the efficiency of placing key appliances in a design, for example, fridge, cooker and sink.
Explain the principles of the work triangle in relation to safety issues in a kitchen.
Consider transport of hot food, and carrying heavy objects.
Discuss the “sequence of use” design principle as applied to kitchen design.
The sequence of use for a right-handed person is from left to right, from the sink to the main work surface to the cooker and to accessory work surfaces.
Outline three examples of the use of anthropometric data in kitchen design.
For example, height of work surfaces, position of cupboards, depth of worktops, circulation space.
Outline psychological human factors data that could be used in kitchen design.
For example, perception of texture, temperature, light and colour.
Discuss the differences in human factors data that may be relevant for a domestic kitchen compared to a commercial restaurant kitchen.
Consider the interaction of the staff involved, heat generated, ventilation, access areas, storage, and health and safety issues.
Discuss how the layout of labelling information for kitchen appliances can be misleading to the user.
For example, microwave ovens often have different labelling for control panels.
Outline physiological human factors data that could be used when designing kitchen products.
For example, viewing distances, pulling strength, lifting strength and turning strength.
Environment: open-plan office (3 hours)
Outline the influence of the psychological human factors of noise and temperature on the design of an open-plan office.
Consider sound-absorbing acoustic partitions, separate noisy equipment, silent phone tones, ventilation flow, static and dynamic tasks.
Discuss how the final design of an open-plan office is a compromise between individual space preferences and standardized design.
Space is often allocated based on standardized tasks or office status, but different individuals have different personal space needs.
Discuss safety considerations that impact on the design of an open-plan office.
For example, cable layout and other tripping hazards, people circulation spaces, storage areas, and fire evacuation plans.
Identify psychological and physiological factors that influence the design of office furniture.
Consider comfort, adjustability, long periods of use and aesthetics.
Outline three examples of the use of anthropometric data in the design of office furniture.
Environment: car (3 hours)
Outline how the location and layout of car controls influence efficient use.
For example, car window controls on the door make it a better design than that of window controls in the centre console.
Discuss how designers have used new technology to redesign the interiors of cars to improve human factors issues.
For example, the use of colours, sound and voice synthesizers to warn the driver of different situations.
Discuss how designers have redesigned the interiors of cars to the benefit of passengers and drivers.
For example, climate control, zoned heating and memory adjusting seats.
Discuss how designers may overlook the implications for human factors when designing multifunctional electronic controls in cars.
As with other electronic appliances, designers can overstep the mark by allowing technology to dictate the design. Many users find multifunctional electronic controls a problem, either because they do not understand them or because the controls are physically too difficult to use.