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Human factors

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Human factors is a term that covers:

  • The science of understanding the properties of human capability (Human Factors Science).
  • The application of this understanding to the design and development of systems and services (Human Factors Engineering).
  • The art of ensuring successful application of Human Factors Engineering to a programme (sometimes referred to as Human Factors Integration).

The term "human factors science/research/technologies" is to a large extent synonymous with the term "ergonomics", having separate origins on either side of the Atlantic Ocean but covering the same technical areas.

In general, a human factor is a physical or cognitive property of an individual or social behavior which is specific to humans and influences functioning of technological systems as well as human-environment equilibriums.

The recognition and study of human factors is important for safety because they can be the cause of serious human errors on the levels of physical behavior and socio-cognitive decision-making ( A.M.Gadomski).

In social interactions, the use of the term human factor stresses the social properties unique to or characteristic of humans.

Human factors involves the study of all aspects of the way humans relate to the world around them, with the aim of improving operational performance, safety, through life costs and/or adoption through improvement in the experience of the end user.

The terms human factors and ergonomics have only been widely used in recent times; the field's origin is in the design and use of aircraft during World War II to improve aviation safety. It was in reference to the psychologists and physiologists working at that time and the work that they were doing that the terms "applied psychology" and “ergonomics” were first coined. Work by Elias Porter, Ph.D. and others within the RAND Corporation after WWII extended these concepts. "As the thinking progressed, a new concept developed - that it was possible to view an organization such as an air-defense, man-machine system as a single organism and that it was possible to study the behavior of such an organism. It was the climate for a breakthrough."[1]

Specialisations within this field include cognitive ergonomics, usability, human computer/human machine interaction, and user experience engineering. New terms are being generated all the time. For instance, “user trial engineer” may refer to a human factors professional who specialises in user trials. Although the names change, human factors professionals share an underlying vision that through application of an understanding of human factors the design of equipment, systems and working methods will be improved, directly affecting people’s lives for the better.

Human factors practitioners come from a variety of backgrounds, though predominantly they are psychologists (engineering, cognitive, perceptual, and experimental) and physiologists. Designers (industrial, interaction, and graphic), anthropologists, technical communication scholars and computer scientists also contribute. Though some practitioners enter the field of human factors from other disciplines, both M.S. and Ph.D. degrees in Human Factors Engineering are available from several universities worldwide.


The Cycle of Human Factors

Human Factors involves the study of factors and development of tools that facilitate the achievement of these goals. In the most general sense, the three goals of human factors are accomplished through several procedures in human factors cycle,[How to reference and link to summary or text] which depicts the human operator (brain and body) and the system with which he or she is interacting. At first point it is necessary to diagnose or identify the problems and deficiencies in the human-system interaction of an existing system. After defining the problems there are five different approaches that can be approached to in order to implement the solution. There are as follows: •Equipment Design: changes the nature of the physical equipment with which human work. •Task Design: focuses more on changing what operators do than on changing the devices they use. This may involve assigning part or all of tasks to other workers or to automated components. •Environmental Design: implements changes, such as improved lighting, temperature control and reduced noise in the physical environment where the task is carried out. •Training the individuals: better preparing the worker for the conditions that he or she will encounter in the job environment by teaching and practicing the necessary physical or mental skills. •Selection of individuals: is a technique that recognizes the individual differences across human in almost every physical and mental dimension that is relevant for good system performance. Such a performance can be optimized by selecting operators who possess the best profile of characteristics for the job. [How to reference and link to summary or text]

Human Factors Science

Human factors are sets of human-specific physical, mental and behavioral properties which either may interact in a critical or dangerous manner with technological systems, human natural environment and human organizations, or they can be taken under consideration in the design of ergonomic human-user oriented equipments. The choice/identification of human factors usually depends on their possible negative or positive impact on the functioning of human-organization and human-machine system.

The human-machine model

see also: human-machine system

The simple human-machine model is of a person interacting with a machine in some kind of environment. The person and machine are both modeled as information-processing devices, each with inputs, central processing, and outputs. The inputs of a person are the senses (e.g., eyes, ears) and the outputs are effectors (e.g., hands, voice). The inputs of a machine are input control devices (e.g., keyboard, mouse) and the outputs are output display devices (e.g., screen, auditory alerts). The environment can be characterized physically (e.g., vibration, noise, zero-gravity), cognitively (e.g., time pressure, uncertainty, risk), and/or organizationally (e.g., organizational structure, job design). This provides a convenient way for organizing some of the major concerns of human engineering: the selection and design of machine displays and controls; the layout and design of workplaces; design for maintainability; and the design of the work environment.

Example: Driving an automobile is a familiar example of a simple man-machine system. In driving, the operator receives inputs from outside the vehicle (sounds and visual cues from traffic, obstructions, and signals) and from displays inside the vehicle (such as the speedometer, fuel indicator, and temperature gauge). The driver continually evaluates this information, decides on courses of action, and translates those decisions into actions upon the vehicle's controls—principally the accelerator, steering wheel, and brake. Finally, the driver is influenced by such environmental factors as noise, fumes, and temperature.

No matter how important it may be to match an individual operator to a machine, some of the most challenging and complex human problems arise in the design of large man-machine systems and in the integration of human operators into these systems. Examples of such large systems are a modern jet airliner, an automated post office, an industrial plant, a nuclear submarine, and a space vehicle launch and recovery system. In the design of such systems, human-factors engineers study, in addition to all the considerations previously mentioned, three factors: personnel, training, and operating procedures.

• Personnel are trained; that is, they are given appropriate information and skills required to operate and maintain the system. System design includes the development of training techniques and programs and often extends to the design of training devices and training aids.

• Instructions, operating procedures, and rules set forth the duties of each operator in a system and specify how the system is to function. Tailoring operating rules to the requirements of the system and the people in it contributes greatly to safe, orderly, and efficient operations.

Human Factors Methods

Methods used to evaluate human factors range from simple questionnaires to more complex and expensive usability labs.

Summary of Human Factors Methods[2]

Name Cost Questions/Evaluations proposed Recommended point of use in design timeline Use of subjects Process Result type
Activity Analysis $$ What are people doing? How much time spent on task? What are the tasks? Early to help frame what is needed in design. As follow up after product is released Use subjects for observation Observe subjects in natural environments, take notes and data Qualitative, observational
Ethnographic Analysis $$ What are people doing? How much time spent on task? What devices or tools does user utilize? Early to help frame what is needed in design. Field observation of subject workspace Look for artifacts, devices, tools, sequences used in subject environment Qualitative, observational
Focus Group $$$$ There are three different types of focus groups: 1. Closed Questions - A yes or no question to gather specific information. 2. Open Ended Questions - To gather more than a yes or no response, an elaboration on their opinions. 3. Probing Questions A follow up question to either the open or closed question to gather more specific information on why they thought a certain way. Anytime Group facilitator, Group of users (6-10) Facilitator has group of users discuss specific topic Most effective feedback from quotes, short clips
Meta Analysis $$ Combine results across studies to draw conclusions/trends for a body of literature After design and studies are completed Previous Studies on specified subject How many studies? Type of testing to use? Looking into direction that literature is going
Persona $ Who are the target groups? Who is being designed for? During planning and design Utilizes statistics of subject groups, possible individual interviews for supplemental data Based on statistics, create Details of archetypes: names, families, pet peeves, jobs, needs, tasks Archetypes that represent actual groups of users and their needs, using specific details to make archetypes real
Subjects in Tandem $$ Discover usability difficulties During planning and design Two subjects Subjects are asked to perform task together while being observed, typically videotaped Videotape of subjects, observational
User as Analyst $$ Open-ended to needs of experimenter Planning, testing or prototype design At least 1 subject User input is taken for development of design Actual user feedback on design
Questionnaire $ Limited in design to user opinion type questions. Many different types of questionnaires may be used including: Multiple Choice – Used when looking to choose a specific response.

Rating Scales – Subjective data on subject’s opinion on a scale of 1-5. Paired Associates – Choosing between two options Ranking – Numerical Ranking 1-10 on usability Open Ended Questions – Used to get subjects opinion where they can write anything Closed Questions – Subject must choose from specific responses Filter Questions – Used to filter questions asked based on previous knowledge or experience.

Early for user opinions on idea. As follow up for feedback on design. No need for face to face interaction; easy to get many subjects Define objectives, make introduction, question types. Accurately reflects user opinions
Think Aloud $$ Reveals problems and attitudes towards design During testing or prototype design. As follow up after product is released. Must be representative of actual user and experience level Subject does specified task and explains what they are doing out loud to trained experimenter An assessment of system through the user's thoughts
Prototyping $ Addresses Design and Layout issues Early; Before computer design or more time consuming developing occurs Typical user to use mock up version Paper prototyping- create simple, hand drawn mockup and make changes until best interface Qualitative, quantitative and observational measurements. Results in a "best prototype"
Wizard of Oz $$$$ How to develop the final software or computer device After conceptualized idea, before final design User is tested on some type of computer design, experimenter acts as computer Experimenter acts as computer in order to test design prior to building working design Manipulate design on the fly to see which design works.
Usability Lab $$$$$ Range adjusts to needs of experimenter; usability, attitudes, etc During testing or prototype design. As follow up after product is released. Representative of actual users Create a false lab to record/view user that is separate from experimenter's room Videotape of subjects, observational, can have raw data recorded and analyzed
Observations $$ The type of this method is data collection. This method is used to monitor an individual or a group of individuals while completing a task and document. These observations can be documented by pencil and paper or by video recording. There are three main types of observations:

Overt Observation – The observers will be watching the subjects but not interfere at all, but their presence is known Covert Observation – The subject is not aware of the observer’s presence. Participant Observation – Usually taken over a large period of time with a group of participants of similar characteristics.

The best time to use this type of method is when time is not a constraint. It is a great way to elicit the information about the environment and is able to observe the steps the subject goes through. Best to be used when you need to see all aspects of the experiment. User is observed by one or more facilitators who are familiar with the experiment Observe subjects in natural environments, take notes and data Qualitative, Observational
Interviews $$ This method is from the data collection type. It is a general method between the subject and the experimenter to gather large amounts of specific information. The only key materials needed are writing utensils and paper or a taper recorder to document the questions and answers in the interview. The three main types of interviews are:

Unstructured – No specific questions to be asked. The interviewer is able to ask any question they want and go in any direction they choose. Semi Structured – There is a set series of questions but the interviewer can direct the focus by asking more relevant questions based on the subject. Structured – Interviewer uses a predetermined set and order of questions with no deviation

When time constraints are not issued and bias can be avoided. It is a great way to get specific information from the subject The facilitator will be one on one with the subject After the experiment concludes the facilitator will ask the subject a series of questions following one of the three types to get user opinions and feelings. Best feedback will be from quotes and the answers to the facilitator's questions.

Problems with Human Factors Methods

Problems in how usability measures are employed include: (1) measures of learning and retention of how to use an interface are rarely employed during methods and (2) some studies treat measures of how users interact with interfaces as synonymous with quality-in-use, despite an unclear relation.[3]

Human Factors Engineering

Human factors engineering focuses on how people interact with tasks, machines (or computers), and the environment with the consideration that humans have limitations and capabilities. Human factors engineers evaluate "Human to Human," "Human to Group," "Human to Organizational," and "Human to Machine (Computers)" interactions to better understand these interactions and to develop a framework for evaluation.

Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them. This is a well known subject of Human Factors within the Engineering field. There are many different ways to determine human computer interaction by usability testing.

Human Factors Engineering (HFE) is the discipline of applying what is known about human capabilities and limitations to the design of products, processes, systems, and work environments. It can be applied to the design of all systems having a human interface, including hardware and software. Its application to system design improves ease of use, system performance and reliability, and user satisfaction, while reducing operational errors, operator stress, training requirements, user fatigue, and product liability. HFE is distinctive in being the only discipline that relates humans to technology.

An Example: Human Factors Engineering Applied to the Military

Before World War II, HFE had no significance in the design of machines. Consequently, many fatal human errors during the war were directly or indirectly related to the absence of comprehensive HFE analyses in the design and manufacturing process. One of the reasons for so many costly errors was the fact that the capabilities of the human were not clearly differentiated from those of the machine.

Furthermore, human performance capabilities, skill limitation, and response tendencies were not adequately considered in the designs of the new systems that were being produced so rapidly during the war. For example, pilots were often trained on one generation of aircraft, but by the time they got to the war zone, they were required to fly a newer model. The newer model was usually more complex than the older one and, even more detrimental, the controls may have had opposing functions assigned to them. Some aircraft required that the control stick be pulled back toward the pilot in order to pull the nose up. In other aircraft the exact opposite was required; namely, in order to ascend you would push the stick away from you. Needless to say, in an emergency situation many pilots became confused and performed the incorrect maneuver, with disastrous results.

Along the same line, pilots were subject to substitution errors due mostly to lack of uniformity of control design, inadequate separation of controls, or the lack of a coding system to help the pilot identify controls by the sense of touch alone. For example, in the early days of retractable landing gear, pilots often grabbed the wrong lever and mistakenly raised the landing gear instead of the flaps. Sensory overload also became a problem, especially in cockpit design. The 1950’s brought a strong program of standardizing control shapes, locations and overload management.

The growth of human factors engineering during the mid- to late-forties was evidenced by the establishment of several organizations to conduct psychological research on equipment design. Toward the end of 1945, Paul Fitts established what came to be known as the Behavioral Sciences Laboratory at the Army Corps Aeromedical Laboratory in Dayton, Ohio. Around the same time, the U.S. Navy established the Naval Research Laboratory at Anacostia, Maryland (headed by Frank V. Taylor), and the Navy Special Devices Center at Port Washington, New York (headed by Leonard C. Mead). The Navy Electronics Laboratory in San Diego, California, was established about a year later with Arnold M. Small as head.

In addition to the establishment of these military organizations, the human factors discipline expanded wihtin several civilian activities. Contract support was provided by the U.S. Navy and the U.S. Air Force for research at several noted universities, specifically Johns Hopkins, Tufts, Harvard, Maryland, Holyoke, and California (Berkeley). Paralleling this growth was the establishment of several private corporate ventures. Thus, as a direct result of the efforts of World War II, a new industry known as engineering psychology or human factors engineering was born.

Why is HFE important to the military?

Until this day, many project managers and designers are still slow to consider Human Factors Engineering (HFE) as an essential and integral part of the design process. This is mostly due to their lack of education on the purpose of HFE. Nevertheless, progress is being made as HFE is becoming more and more accepted and is now implemented in a wide variety of applications and processes. The U.S. military is particularly concerned with the implementation of HFE in every phase of the acquisition process of its systems and equipment. Just about every piece of gear, from a multi-billion dollar aircraft carrier to the boots that Servicemembers wear, goes at least in part through some HFE analyses before procurement and throughout its lifecycle.

Lessons learned in the aftermath of World War II prompted the U.S. War Department (now U.S. Department of Defense) to take some steps in improving safety in military operations. The importance attached to HFE by the U.S. military is outlined in the U.S. Department of Defense regulation DoD 5000.2-R (Paragraph 4.3.8) which requires that a comprehensive management and technical strategy for human systems integration (HSI) be initiated early in the acquisition process to ensure that human performance is considered throughout the system design and development process.

HFE applications in the U.S. Army

In the U.S. Army, the term MANPRINT is used as the program designed to implement HSI. The program was established in 1984 with a primary objective to place the human element (functioning as individual, crew/team, unit and organization) on equal footing with other design criteria such as hardware and software. The entry point of MANPRINT in the acquisition process is through requirements documents and studies.

While many Army documents contain references to MANPRINT, the MANPRINT program is governed by AR 602-2, "Manpower and Personnel Integration (MANPRINT). AR 602-2 prescribes policies and assigns responsibilities for the program. The MANPRINT Web Page at www.manprint.army.mil is a valuable source of information and guidance on MANPRINT.

What is MANPRINT?

MANPRINT (Manpower and Personnel Integration) is a comprehensive management and technical program that focuses attention on human capabilities and limitations throughout the system’s life cycle: concept development, test and evaluation, documentation, design, development, fielding, post-fielding, operation and modernization of systems. It was initiated in recognition of the fact that the human is an integral part of the total system. If the human part of the system can't perform efficiently, the entire system will function sub-optimally.

MANPRINT's goal is to optimize total system performance at acceptable cost and within human constraints. This is achieved by the continuous integration of seven human-related considerations (known as MANPRINT domains) with the hardware and software components of the total system and with each other, as appropriate. The seven MANPRINT domains are: Manpower (M), Personnel (P), Training (T), Human Factors Engineering (HFE), System Safety (SS), Health Hazards (HH), Soldier Survivability (SSv). They are each expounded on below:

Manpower (M)

Manpower addresses the number of military and civilian personnel required and potentially available to operate, maintain, sustain, and provide training for systems in accordance with Title 10, U. S. Code Armed Forces, Sec. 2434. It is the number of personnel spaces (required or authorized positions) and available people (operating strength). It considers these requirements for peacetime, conflict, and low intensity operations. Current and projected constraints on the total size of the Army/organization/unit are also considered. The MANPRINT practitioner evaluates the manpower required and/or available to support a new system and subsequently considers these constraints to ensure that the human resource demands of the system do not exceed the projected supply.

Personnel (P)

Manpower and personnel are closely related. While manpower looks at numbers of spaces and people, the domain of personnel addresses the cognitive and physical characteristics and capabilities required to be able to train for, operate, maintain, and sustain materiel and information systems. Personnel capabilities are normally reflected as knowledge, skills, abilities, and other characteristics (KSAOs). The availability of personnel and their KSAOs should be identified early in the acquisition process and may result in specific thresholds. On most systems, emphasis is placed on enlisted personnel as the primary operators, maintainers, and supporters of the system. Personnel characteristics of enlisted personnel are easier to quantify since the Armed Services Vocational Aptitude Battery (ASVAB) is administered to potential enlistees.

While normally enlisted personnel are operators and maintainers; that is not always the case, especially in aviation systems. Early in the requirements determination process, identification of the target audience should be accomplished and used as a baseline for assessment. Cognitive and physical demands of the system should be assessed and compared to the projected supply. MANPRINT also takes into consideration personnel factors such as availability, recruitment, skill identifiers, promotion, and assignment.

Training (T)

Training is defined as the instruction or education, on-the-job, or self development training required to provide all personnel and units with their essential job skills, and knowledge. Training is required to bridge the gap between the target audiences' existing level of knowledge and that required to effectively operate, deploy/employ, maintain and support the system. The MANPRINT goal is to acquire systems that meet the Army's training thresholds for operation and maintenance. Key considerations include developing an affordable, effective and efficient training strategy (which addresses new equipment, training devices, institutional, sustainment, and unit collective tactical training); determining the resources required to implement it in support of fielding and the most efficient method for dissemination (contractor, distance learning, exportable packages, etc.); and evaluating the effectiveness of the training.

Training is particularly crucial in the acquisition and employment of a new system. New tasks may be introduced into a duty position; current processes may be significantly changed; existing job responsibilities may be redefined, shifted, or eliminated; and/or entirely new positions may be required. It is vital to consider the total training impact of the system on both the individuals and the organization as a whole.

Human Factors Engineering (HFE)

The goal of HFE is to maximize the ability of an individual or crew to operate and maintain a system at required levels by eliminating design-induced difficulty and error. Human factors engineers work with systems engineers to design and evaluate human-system interfaces to ensure they are compatible with the capabilities and limitations of the potential user population. HFE is conducted during all phases of system development, to include requirements specification, design and testing and evaluation. HFE activities during requirements specification include: evaluating predecessor systems and operator tasks; analyzing user needs; analyzing and allocating functions; and analyzing tasks and associated workload. During the design phase, HFE activities include: evaluating alternative designs through the use of equipment mockups and software prototypes; evaluating software by performing usability testing; refining analysis of tasks and workload; and using modeling tools such as human figure models to evaluate crew station and workplace design and operator procedures. During the testing and evaluation phase, HFE activities include: confirming the design meets HFE specification requirements; measuring operator task performance; and identifying any undesirable design or procedural features.

System Safety (SS)

System Safety is the design features and operating characteristics of a system that serve to minimize the potential for human or machine errors or failures that cause injurious accidents. Safety considerations should be applied in system acquisition to minimize the potential for accidental injury of personnel and mission failure.

Health Hazards (HH)

Health Hazards addresses the design features and operating characteristics of a system that create significant risks of bodily injury or death. Along with safety hazards, an assessment of health hazards is necessary to determine risk reduction or mitigation. The goal of the Health Hazard Assessment (HHA) is to incorporate biomedical knowledge and principles early in the design of a system to eliminate or control health hazards. Early application will eliminate costly system retrofits and training restrictions resulting in enhanced soldier-system performance, readiness and cost savings. HHA is closely related to occupational health and preventive medicine but gets its distinctive character from its emphasis on soldier-system interactions of military unique systems and operations.

Health Hazard categories include acoustic energy, biological substances, chemical substances, oxygen deficiency, radiation energy, shock, temperature extremes and humidity, trauma, vibration, and other hazards. Health hazards include those areas that could cause death, injury, illness, disability, or a reduction in job performance.

Organisational and Social

The seventh domain addresses the human factors issues associated with the socio-technical systems necessary for modern warfare. This domain has been recently added to investigate issues specific to Network Enabled Capability (NEC) also known as Network Centric Warfare (NCW). Elements such as dynamic command and control structures, data assimilation across mulitple platforms and its fusion into information easily understood by distributed operators are some of the issues investigated.

A soldier survivability domain was also proposed but this was never fully integrated into the MANPRINT model.

Domain Integration

Although each of the MANPRINT domains has been introduced separately, in practice they are often interrelated and tend to impact on one another. Changes in system design to correct a deficiency in one MANPRINT domain nearly always impact another domain.

Human Factors Integration

Areas of interest for human factors practitioners may include: training, staffing evaluation, communication, task analyses, functional requirements analyses and allocation, job descriptions and functions, procedures and procedure use, knowledge, skills, and abilities; organizational culture, human-machine interaction, workload on the human, fatigue, situational awareness, usability, user interface, learnability, attention, vigilance, human performance, human reliability, human-computer interaction, control and display design, stress, visualization of data, individual differences, aging, accessibility, safety, shift work, work in extreme environments including virtual environments, human error, and decision making.

Real World Applications of Human Factors - MultiModal Interfaces

Multi-Modal Interfaces

In many real world domains, ineffective communication occurs partially because of inappropriate and ineffective presentation of information. Many real world interfaces both allow user input and provide user output in a single modality (most often being either visual or auditory). This single modality presentation can often lead to data overload in that modality causing the user to become overwhelmed by information and cause him/her to overlook something. One way to address this issue is to use multi-modal interfaces.

Reasons to Use Multimodal Interfaces

-Time Sharing – helps avoid overloading one single modality -Redundancy – providing the same information in two different modalities helps assure that the user will see the information

-Allows for more diversity in users (blind can use tactile input; hearing impaired can use visual input and output)

-Error Prevention – having multiple modalities allows the user to choose the most appropriate modality for each task (for example, spatial tasks are best done in a visual modality and would be much harder in a olfactory modality)

Examples of Well Known Multi-Modality Interfaces

- Cell Phone – The average cell phone uses auditory, visual, and tactile output through use of a phone ringing, vibrating, and a visual display of caller ID.

- ATM – Both auditory and visual outputs

Early Multi-Modal Interfaces by the Experts

-Bolts “Put That There” – 1980 – used speech and manual pointing

- Cohen and Oviatt’s “Quickset” – multi user speech and gesture input

Worker Safety and Health

One of the most prevalent types of work related injuries are musculoskeletal disorders. Work-related musculoskeletal disorders (WRMDs) result in persistent pain, loss of functional capacity and work disability, but their initial diagnosis is difficult because they are mainly based on complaints of pain and other symptoms. [4] Every year 1.8 million U.S. workers experience WRMDs and nearly 600,000 of the injuries are serious enough to cause workers to miss work. [5] Certain jobs or work conditions cause a higher rate worker complaints of undue strain, localized fatigue, discomfort, or pain that does not go away after overnight rest. These types of jobs are often those involving activities such as repetitive and forceful exertions; frequent, heavy, or overhead lifts; awkward work positions; or use of vibrating equipment. [6] The Occupational Safety and Health Administration (OSHA) has found substantial evidence that ergonomics programs can cut workers' compensation costs, increase productivity and decrease employee turnover.[7] Therefore, it is important to gather data to identify jobs or work conditions that are most problematic, using sources such as injury and illness logs, medical records, and job analyses.[6]

Job analyses can be carried out using methods analysis, time studies, work sampling, or other established work measurement systems.

  • Methods Analysis is the process of studying the tasks a worker completes using a step-by-step investigation. Each task in broken down into smaller steps until each motion the worker performs is described. Doing so enables you to see exactly where repetitive or straining tasks occur.
  • Time studies determine the time required for a worker to complete each task. Time studies are often used to analyze cyclical jobs. They are considered “event based” studies because time measurements are triggered by the occurrence of predetermined events. [8]
  • Work Sampling is a method in which the job is sampled at random intervals to determine the proportion of total time spent on a particular task. [8] It provides insight into how often workers are performing tasks which might cause strain on their bodies.
  • Predetermined time systems are methods for analyzing the time spent by workers on a particular task. One of the most widely used predetermined time system is called Methods-Time-Measurement or MTM. Other common work measurement systems include MODAPTS and MOST.

References

  1. ↑ Porter, Elias H. (1964). Manpower Development: The System Training Concept. New York: Harper and Row, p. xiii.
  2. ↑ Stanton, N.; Salmon, P., Walker G., Baber, C., Jenkins, D. (2005). Human Factors Methods; A Practical Guide For Engineering and Design., Aldershot, Hampshire: Ashgate Publishing Limited.
  3. ↑ Hornbaek, K (2006). Current Practice in Measuring Usability: Challenges to Usability Studies and Research, International Journal of Human-Computer Studies.
  4. ↑ Template:Cite article
  5. ↑ Template:Cite article
  6. ↑ 6.0 6.1 Workplace Ergonomics: NIOSH Provides Steps to Minimize Musculoskeletal Disorders. URL accessed on 2008-04-23.
  7. ↑ Charles N. Jeffress (October 27, 2000). BEACON Biodynamics and Ergonomics Symposium.
  8. ↑ 8.0 8.1 Thomas J. Armstrong (2007). Measurement and Design of Work.

Additional Reading

  • Wickens, C.D.; Lee J.D.; Liu Y.; Gorden Becker S.E. (1997). An Introduction to Human Factors Engineering, 2nd Edition, Prentice Hall.
  • Wickens, C. D., Sandry, D. L., & Vidulich, M. (1983). Compatibility and resource competition between modalities of input, central processing, and output. Human Factors, 25, 227-248.
  • Oviatt, S.L. & Cohen, P.R., (2000, March). Multimodal systems that process what comes naturally. Communications of the ACM, 43(3), 45-53. New York: ACM Press.
  • Sarter, N.B., 2002. Multimodal information presentation in support of human-automation communication and coordination. In: Salas, E. (Ed.), Advances in human performance and cognitive engineering

See also

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