Ergonomics Quiz 5
effective rating characteristics
-Accuracy in rating: the first and most important characteristics of any rating system (within ± 5% of the standard average) -Performance rating: Need to consider speed, dexterity, rhythm, coordination, and effectiveness -Frequency of rating: (Depends on the cycle time) (Short-cyclic element - little deviation in operator performance is expected during the course of the average length study (15-30 min). Thus, it is ok to rate the entire study) (For longer study (>30 min) operator performance vary. Thus, each element should be rated)
variable fatigue allowances
-Affected by: -Working condition (noise, heat, humidity) -Nature of work (posture, muscular exertion, tediousness, and general health of the worker) -How to measure ? -Finding the decrease in production throughput during the working period (continuous work) F=(T - t) * 100 / T F - Coefficient of fatigue T - operation time required at the end of continuous work t - operation time required at the beginning of the beginning of the continuous work
methods for developing standard allowance data
-Direct time study - observers (analysts) study several workers for a long period of time (disadvantages: expensive, small sample) -Work sampling studies - taking a large number of random observations (study of about two weeks)
synthetic rating
-Does not rely on the judgment of a time study observer (consistent results) -Evaluating operation rate by comparing the actual elemental observed times to times developed through fundamental motion data
muscular force
-Fatigue allowances can be formulated on two important physiological principles: 1) Muscle Fatigue, and 2) Muscle Recovery after Fatigue Initiated by Rohmert (1960) efforts: -Reduction in maximum strength for static holds that exceeds 15% of MVC -Longer static contraction leads to greater reduction in muscle strength -Individual muscle variations are minimized if forces are normalized to individual's MVC -Recovery is a function of the degree of fatigue
physiological evaluation of performance level
-Measuring physiological variables such as: heart activity, Oxygen consumption per time unit which are affected from worker performance -Using electronic equipment which has minimum interference with the worker's work
ADA reasonable acommodation
-Modification to existing facilities -Job restructuring -Modified work schedules (including part-time) -Reassignment to vacant positions -Modified or new equipment and assistive devices -Adjustment to examinations and training policies -Provisions for readers and interpreters
objective rating
-One problem with former methods: work difficulty is not taken into consideration during rating evaluation -Factors influence difficulty: 1) Amount of body used, 2) Foot pedals, 3) Bimanualness, 4) Eye hand coordination, 5) Handling or sensory requirements, 6) Weight handled or resistance encountered -Solution: Two factors: pace rating factor (P) and job difficulty adjustment factor (D) Overall rating, R = P * D
constant allowances
-Personal needs - traveling for the drinking fountain, restroom, etc. (Partially depend on the working condition) About 5% (4.6-6.5 percent) -Basic fatigue - the fix part of the allowance due to fatigue. Given to a worker doing light job in a very good environmental and working conditions. About 4% Most operators are given an initial 9 percent constant allowance
time study cyclic work
-Rating evaluation may be written once in a couple of cycles -Elements times: 0.04min (short), 0.25min (reasonable) -Denoting non-cyclic and foreign elements -The breakpoint between elements should be clear (touch, push, etc.). -Exception observations should be eliminated (to be explained later)
types of rating methods
-Speed rating: fastest and simplest method -The Westinghouse System: One of the oldest methods developed by Westinghouse Electric Corporation -Synthetic rating: Developed by Morrow (1946) - computes ratings based on motion data -Objective rating: Developed by Mundel & Danner (1994), considers pace and task difficulty
special allowances
-Unavoidable delays -Supervisor interruptions -Material irregularities -Stochastic behavior in production (machine interference - maintenance workers) -Avoidable delays (extra idleness, social visits) -Extra allowances - documentation, cleanup, attention time
time study on non cyclic work
-Use continuous timing (and not snapback technique) -Divide the task into relatively large elements -Write the evaluated performance rate at the end of each element -Multiply the observed time with the rate and summarize the data
performance rating
-Very important step in work measurement procedure -Also most subject to criticism -Very dependent on the experience, training, and judgment of the work measurement analyst -After calculating the normal time, one additional step must be performed to arrive at a fair standard
other pre-employment screening
-anthropometry (only minimal associations found between anthropometric measures and injury risks) -range of motion -muscle strength -general fitness (some evidence that good health is associated with lower risk of chronic LBP)(some studies have shown cardiovascular fitness is not predictive of future injury)
aspects of worker compensation
-claims must be filed within one year of the time employee becomes self-aware of a work-related injury -premiums charged by insurers are based on risk insurer feels it takes in providing coverage: based on past experience, past losses, possible future losses -some common aspects between states: must arise out of employment, occurs during course of employment -limitations: intoxication, intentionally self-inflicted -types of disabilities: -temporary-partial (incomplete reporting in many states) -temporary-total (majority of cases) -permanent-partial (awards may be paid for life) -permanent-total (awards may be paid for life) -monetary benefits vary by state
effective training
-create an environment where trainees can: (learn the requisite knowledge, skills, attitudes)(practiec applying the learned knowledge, skills, and abilities KSAs)(receive constructive and timely feedback)
workforce trends
-demographic changes (aging workforce, increasing number of women, increasing number of dual-career couples) -changes in the structure of work (increasing tech, rise of technical, professional, "white collar" jobs) -diversity of work tasks
ADA 2
-designed to remove barriers that prevent qualified individuals with disabilities from same employment opportunities available to able-bodied -where an individual's disability creates a barrier to employment, the employer must consider whether a reasonable accommodation could remove that barrier -if functional impairment impedes job performance, employer must take steps to reasonably accommodate the impediment, unless doing so poses an undue hardship
rules for performing time study
-dont comment to the worker during teh task -stand beside the worker -write every evejt -have a good position to observe -behave yourself -stop the study if the worker seems to be under pressure and it affects his/her work
avoiding negligence
-ergonomists need to do jobs in professional and responsible manner and be able to prove it -one significant aspect in decisions: failure to communicate -where there is proof of interaction, difficult to find facts to support punitive damage awards -retain contact records -do follow-up inquires -document all professional, supervisory, and worker involvement in ergonomic process -keep track of all announcements, postings, etc.
worker selection philosophy 2
-except for a few situations, pre-employment health screening is not acceptable -testing a person to assure they can successfully and safely perform very well documented and essential functions of a job may be allowed, as long as the testing process is not biased -we have pre-placement screening (screening someone who has already been hired to determine his/her suitability for one of the several alternatives
Why evaluate worker capacity?
-find high risk workers -improve performance -assess return to work status -affirmative action for women, older workers, and physically impaired -cheaper than changing job?
arguments for the standard
-fulfills need for comprehensive approach to WMSDs -establish formal lines of communication -increased employee participation -encourages systematic and iterative process -ensures employee is informed, and their costs are minimized -ensures supervisors understand situation -if not "forced", companies will not protect employees
patient history and physical exam
-identify high risk people -importance of previous musculoskeletal problems (80-85% of people with lower back pain have recurrence)(3x increase in risk of LBP over 1 year if there is pervious history) -should previous back pain be used as a risk indicator? (applicants may be dishonest, prevalence of LBP is so high causing many older workers to be refused, sensitivity of previous LBP is estimated 25%) -previous LBP with other tests may increase predictive value
personnel selection approach
-identify job demands (job analysis for knowledge, skills, abilities), performance criteria -measure workers' capabilities/attributes for cognitive ability, physical abilities like strength, endurance, and fitness, and personality
developing training programs
-identify training goals/ objectives -determine needs of your audience -develop delivery plan: method and content -deliver training -measure effectiveness (individual level, training transfer, organizational level, short vs. long term)
motivation for training
-knowledge economy (increasing number of knowledge worker, intellectual component of many jobs has increased, shorter shelf life of knowledge, shorter shelf life of knowledge)
why do we need a time study?
-methods improvement -determine time standards
worker selection philosophy 1
-muscle strength can vary tenfold between different workers -with variation, designing a job to accommodate the weakest workers who might be interested in performing a task may not be the most desirable approach from a cost-benefit and technical perspective -alternative? carefully select the most appropriate workers for specific job -in the US, it became illegal to discriminate against an individual on the basis of gender, age, race, and perceived disability
audience needs
-need to know why they should learn something -need to be self-directed and decide for themselves what they want to learn -have a far greater volume and different quality of experiences -become ready to learn when they experience a life situation where they need to know -enter into the learning process with a task centered orientation to learning -motivated to learn by both extrinsic and intrinsic motivation
important aspects of worker compensation
-non-uniformity: 57 WC legal structures, each different -coverage: approx. 99% of all US wage and salary workers, which is 90% of all jobs (some states do not require coverage for <10 employees -insurance: very large companies self-insure, claims for work-related MSDs have risen dramatically
product liability
-product liability is an area of law in which individuals with expertise in human factors make significant contributions addressed areas: -product design defects -manufacturing defects -failures to warn
arguments against the standard
-program is a reactive approach to control and prevention -lack of research to support all the requirements -lack of empirical evidence to guide control -may require significant economic resources -may actually increase resistance toward ergonomics -vague wording may lead to problems in enforcement and associated litigation
key aspects in motivation work compliance in prevention
-recognizing the injury problem and employee's role -acquiring knowledge of the spine and injury risk factors -understanding the relevance of problem to workers specific jobs -learning to alter behavior through knowledge of safe methods -practice in new alternative methods -followup at the workplace
OSHA ergonomics program standard
-reduce the large number and severity of WMSDS -industries required to set up an ergonomics program to identify and control hazards that are likely to be causing or contributing to the WMSDs -the specific king of program depends on the extent of the problem why is it needed now? -WMSDs account for 35% of all lost-work day injuries, 1$ out of every 3$ spent for WC, >15-20billion$ in WC -WMSDs are preventable -scientific evidence supports standard
criteria for use of physical assessment screening
-safety -reliability/repeatability -quantitative -relatedness -practicality -predictive ability
ergonomic professional standards
-standard of care for ergonomics professionals -obligation to act, in the practice of their profession, with that degree of care, skill, and diligence commonly exercised by similar professionals under similar circumstances -failure to do so can be considered negligence, reckless, or worse -if that behavior causes harm to a worker, lawyers appear -simply stated, a cause of action is based on: a duty, that is breached, causing injury
ADDIE: analysis phase
-the instructional problem is clarified. -the instructional goals and objectives are established -the learning environment and learner's existing knowledge and skills are identified
training to solve
-worker selection issue -skill deficiency -lack of ability -lack of motivation -safety issues
criteria for successful speed rating evaluation
1. Experience in the class of work performed (is a should) 2. Use of synthetic benchmark on at least two of the elements performed 3. Selection of an operator who gives performances between 85 and 115 of standard pace 4. Use of the mean value of three or more independent studies
worker training
3 major economic approaches for improving safety: personnel training, personnel selection, job design -the first two fit the person to the job, the latter fits the job to the person
performance factor
= Ft / O P - Performance or rating factor Ft - Fundamental Motion Time O - observed average actual time value for the same element
standard time
=(Observed Time) ( Rating Factor) + (Observed Time) ( Rating Factor) (PFD Allowance) = (Observed Time)(Rating Factor)(1+ PFD Allowance) Observed Time: time you actually record for the task Rating Factor: the effort in which a worker is working (remember working at 100% is not recommended) PFD Allowance: Personal, Fatigue and Delays
standard time
=NT+NT*allowance =NT(1+allowance)
t (for given accuracy)
=[(E)(n^.5)/s]
n (for given accuracy)
=[(t)(s)/E]^2
E (for given conf. level)
=[(t)(s)/n^.5] or =accuracy*xbar
westinghouse system of rating
A four-factor system for rating operator: -Skill: "Proficiency at following a given method". Skills get better over time due to increased familiarity. Skill decreases over time due to some impairment in physical or psychophysical factors, e.g., failing eyesight, failing reflexes, and the loss of muscular strength. -Effort: "Demonstration of the will to work effectively", representative of the speed with which skill is applied to complete the task -Conditions: Affecting worker, not operation, e.g., temperature, noise - NOT poor tools, or materials -Consistency: less variability in elemental times that constantly repeat
# cycles
Confidence level - the probability that an interval about a sample statistic actually includes the population parameter (certainty) Accuracy - the closeness of agreement between an observed value and an accepted reference value use t for n<30
ADA, americans with disabilities act
July 1990 -need: more than 43 million americans have one or more physical or mental disabilities, aging population and better medical care -> longer term survival of disabled -ADA: "the disabled" as a whole "occupy an inferior status in our society and are severly disadvantaged socially, vocationally, economically, and educationally" -purpose: to provide a national mandate to eliminate discrimination against persons with disabilities. Provides clear, strong, consistent, enforceable standards addressing discrimination against disabled. Federal Government enforces the Act
direct time study, issues
Methods improvement Selection of the examined workers Explanation (union, managers, workers) Collecting and recording information Task division into elements (accuracy/cost): Better understanding of the studied task, Helps to identify unproductive elements and eliminate them, Enables separate treatment for each work element, Enables to build standard times for basic elements and use it later on, Enables work planning improvement
specificty
TN/ (FP+TN)*100
sensitivity=
TP/ (TP+FN)*100
positive predictive value=
TP/ (TP+FP)*100
ratings
The assignment of a percentage to the operator's average observed time, based on the actual performance of the operator as compared to the observer's conception of standard performance
observed time
The elemental time for one cycle, obtained either directly (snapback) or by subtracting successive watch times (continuous)
normal time
The time required for the standard operator to perform the operation when working at a standard pace, without delay for personal reasons or unavoidable circumstances =OT*R/100
element
a division of work that can be measured with stopwatch equipment and that has readily identified terminal points
work sampling
a method of analyzing work by taking a large number of observations at random intervals, to establish standards and improve methods
time study
a process for measuring the required time for performing a given task, by a given method, by a trained worker, working in a normal pace
predictive value
ability of test to predict who is at risk of injury -depends on sensitivity, specificity, and prevalence of the disease
allowances
additional time added to the normal time for creating the standard time -Allowances are adjustment of the standard time to compensate loses due to: Personal needs, Fatigue. Unavoidable delays
ADDIE: design phase
address learning objectives, assessment instruments, exercises, content, subject matter analysis, lesson planning and media selection -should be systematic and specific.
OSHA Act
basic components: -standards: establish and maintain a system to legislate specific standards for known occupational hazards -general duty clause: it is the employers responsibility to furnish each employee employment and a place of employment free from recognized hazards that are causing or are likely to cause death or serious physical harm -record keeping: the OSHA act requires all places of employment to maintain substantial records of occupational injury and accidents and to maintain these records on site for OSHA inspections
what to teach?
basic justified guidelines -be in good shape, think before acting, avoid twisting
watch readout
column for recording watch readout
before worker compensation
common law obligations between employers and employees based on the idea that worker: -free to choose employment -knowledgeable of hazards -free to accept or reject risks (employers defense) employers must provide employees with: -safe place to work -safe tools to perform work -knowledge of any hazards not immediately apparent -competent fellow employees and supervisors -rules by which all could perform safely (plaintiff's case)
ADDIE: development phase
create and assemble the content assessts as planned in the design phase
primary approaches to reduce manual material handling
ergonomic job design, worker selection, and worker training -alone are not effective controls for lower back pain
element analysis
every element must have an easily identifiable starting and ending point 1/4 min is reasonable for element -relative frequency included
types of allowances
fatigue allowances (personal needs, basic fatigue, variable fatigue) and special allowances (unavoidable delays, avoidable delays, extra allowances, policy allowance)
sensitivty
few screening or selection procedures have had formal evaluation of accuracy, sensitivity, etc. sensitivity: -measure of the test's ability to identify workers who will develop injury or disease in the future -sensitivity of 95%: 95/100 with risk of risk factors will have positive test
other training approaches
fitness, strength and flexibility training -it is reasonable to assume that higher physical fitness should be associated with greater ability to perform manual lifting without injury -some evidence that weaker workers have higher occurrence of musculoskeletal injury (others say strongest injured more) -flexibility poor predictor of LBP
OSHA ergonomics guidelines
general: -provide management support -involve employees -identify problems -implement solutions -address reports of injuries -provide training -evaluate efforts*
ergonomic technical standards
industry: ASTM, IEEE US national: ANSI, NSC, SAE International: ISO, EU Military: MIL US standards are voluntary International standards can be mandatory
ADDIE model
instructional design model -Analysis: audience, learning styles, personality, learning goals, constraints, environment, resources, timeframe, expectations -Design: skills, knowledge or attitudes, strategies, assessment plans, learning theories -Develop: course materials, outline, multimedia -Implement: prepare learners, prepare faculty, prepare environment, deliver course -Evaluate: reaction, learning, behavior, results
standard performance
level of performance attained by a thoroughly experienced operator working under customary conditions at a pace neither too fast nor too slow, but representative of one that can be maintained throughout the day -freq. distribution will be a normal curve
types of elements
manual/machine cyclic/non cyclic fixed time/ variable time work/ foreign avoidable/ unavoidable unproductive elements
specificity
measures of test's accuracy in correctly identifying workers who will not develop problem in the future -specificity of 95%: out of 100 people who report no injuries after working for a certain length of time, 95 had been predicted to incur no injuries
foreign elements
missed reading observed operator oriented problem (fumble, tool maintenance)
speed rating guide
only considers speed (rate of work per unit time) -Comparing actual work against that of a conceptual "normal worker" -The evaluator should be able to differentiate between type of tasks - experience and practice
Tort Law
plaintiff must substantiate that: -the defendant owed the plaintiff a duty of care -the defendant breached that duty by his or her conduct -the defendant's conduct caused the injury to the plaintiff
hawthorne effect
positive results when persons are treated with actions that are actually ineffective, but which the subjects react to positively because of the show of concern and/ or interest -consultants "success"
ADDIE: implementation phase
procedure for training the facilitators and learners is developed
cycle
set of elements composing a job
ADDIE: evaluation phase
summative evaluation consists of tests designed for domain specific knowledge and providing opportunities for feedback from the users which were identified
training
systematic acquisition of knowledge, skills, and attitudes that lead to improved performance in a specific environment (cognitive and behavioral change)
OSHA logs
the Occupational Safety and Health Act of 1970 requires certain employers to prepare and maintain records of work related injuries and illnesses (companies >10 employees) -log of work (Form 300)-related injuries and illnesses: classify injuries/illnesses and note extent and severity of each case -summary (Form 300A): totals for the year in each category, post in a visible location so employees are aware of injuries/illnesses in their workplace Injury and Illness Incident Report (Form 301): complete within 7 calendar days after receiving information about the occurance
performance rating
the assignment of a percentage to the operator's average observed time, based on the actual performance of the operator as compared to the observer's conception of standard performance
allowance
the time added to procedure to provide for personal delays, unavoidable delays, and fatigue
continuous
time keeps running, you just take readings as the clock goes (easy to use, works well for large number of elements, but easy to miss elements, less precise) -considered superior to snapback -no time lost
standard time
time required by an average worker, working at a normal pace, to complete a specified task using a prescribed method
snapback
timing an individual element (works will with larger or few elements, more accurate, but hard to perform for tasks involving several elements) -omits delays, time must be summed
intentional tort
tort: wrongful act, injury, or damage for which civil action can be brought (intentional tort claim alleges that the employers intended to harm the employee) to establish intent: -knowledge by employer of existence of danger -knowledge that exposure to danger will cause harm with substantial certainty -with this knowledge, required employee to continue performance
element
unit of work
worker compensation
until recently, compensation required the injury to be traced to a time, place, and cause, thus excluding many work-related injuries
OSHA logs 2
work related? "If an event or exposure in the work environment caused or contributed to the condition or significantly aggravated a preexisting condition." which to record? those that result in: death, loss of consciousness, days away from work, restricted activity or job transfers, medical treatment beyond first aid or any significant injury/illness diagnosed by a physician
methods for creating time standards
work sampling-task level direct time study (cyclic and non cyclic work)- work element level synthetic data (standard data systems-work element level and predetermined times-basic motion element levels) indirect methods
