Evaluation of Inter-rater Reliability for Movement and Posture Observations of workers in an Audio Compact Cassette Plant Dararat Techakamolsuk Pornchai Sithisarankul

INCIDENCE OF WORK-RELATED MUSCULOSKELETAL DISORDERS : social security office, Ministry of Labor and social welfare 1998

 Ergonomics is centered on the person  The equipment itself can be important if the person must operate, service, install, and/or repair that equipment  The application of this knowledge to the workplace is essential to order to enhance productivity and to increase the social responsibility of the firm

Laboratory and epidermiologic studies : association between various work-related musculoskeletal disorders and  1.exposure to highly repetitious or static work  2. work requiring high force  3. Non –neutral position or postures  4. awkward postures  5. localized contact pressure  6.vibration  7. cold

 The ergonomic exposures have been assesses by questionnaires PROBLEM :the reliability of self-reported physical exposures have been mixed.  Observational methods continue to be used commonly, especially to assess ergonomic stresses.

MATERIALS AND METHODS  Subjects - four observers (A,B,C and D) indepentdently evaluated 23 workers  using a procedure that included observations of 27 movements and 11 postures from the adapted observational check list  around april 2000  in an audio compact cassette plant, area of molding department, audio assembly area and audio package department

MATERIALS AND METHODS Instrument The ergonomics exposure data : on a onsite observation check list  information to identify each job observed (plant, department, operation number )  day of evaluation  the picture 1-28 for evaluation of movement and work posture

The pictures on check list movement of organs in working

All of them were evaluated in the topic of 1. Repetitions  very often - twice or more in one minute  often - once for each period of 1-3 minutes  occational- once in more than 3 minutes

2. speed  Very fast - close to the maximum speed that can be repeatedly performed by the worker for a given manufacturing operation.  Moderate- is the speed that most resembles natural body movements  Slow- is a speed that is notoriously lower than the moderate

3. Forceful exertion  Much - similar to the maximum value that can be maintenanced during one half of a minute  Moderate- similar to the maximum that can be maintenanced during a period lasting from 1 to 3 minutes  Little- any force that can be maintained for more than 3 minutes

the pictures of onsite observation on posture check list

All were evaluated in the topic of 1.Posture time ( accumulated time during daily journey) :  Between 0 and 1 hour  Between 1 and 3 hour  More than 3 hours

2. Forceful Exertion  Much - similar to the maximum value that can be maintenanced during one half of a minute  Moderate- similar to the maximum that can be maintenanced during a period lasting from 1 to 3 minutes  Little- any force that can be maintained for more than 3 minutes

3. Kind of force applied : Pushing Pulling Twisting the body  Each task was observed for each cycle at least 3 minute  watching all tasks in each cycle at least once time before beginning to count and record specific movements and postures

Data analysis methods  Interrater agreement on the frequency per cycle, speed of motion and forceful exertion of each of the the 17 movements  Interrater agreement on the accumulated time, forceful exertion and kind of force applied of each of the 11 postures

Data analysis methods  evaluated using statistical approaches : proportion of agreement and kappa  performed using SPSS 9.0 for window

Measuring agreement  The simplest calculation : proportion of agreement( the sum of the frequencies along the main diagonals of contingency table)  Kappa ( k ) is a measure of agreement that does account for chance  kappa substracts the proportion of agreement that could be expected by chance alone from the observed proportion of agreement

Example … topic…. Repetition of pic.2

 Percent agreement = 22/27 = (81.48 %)  number of agreement expected just by chance = 9.44  very often = (11*10) /27 = 4.07  often = ( 12*11)/27 = 4.44  Occational = ( 5*5)/ 27 = 0.93  proportion of the total 9.44/ 27 = 0.35  calculate the agreement as ( ) / ( )= 0.70 = KAPPA

Measuring agreement  Kappa has a maximum of 1.00 when agreement is perfect  a value of zero indicates no agreement better than chance  negative values show worse than chance agreement which is unlikely

Kappa ( k )  Value of k Strength of agreement  <0.20 Poor  Fair  Moderate  0.61 –0.80 Good  0.81 –1.00 Very good

Mathematics for kappa  Kappa is calculated from the observed and expected frequencies on the diagonal of a square table frequencies  n observations in g categories : the observed proportional agreement is g  P o = i =1 f Ii / n

Mathematics for kappa  f ii is the number of agreements for categories i : The expected proportion of agreements by chance is given by g  P e = i =1 r i c i / n 2 The index of agreement, kappa, is given by  K= Po – Pe / 1 – Pe The approximate standard error of k is  Se(k )= P o( 1- Po ) / n(1 – Pe) 2 95% confidence interval  K Se(k ) to k Se(k )

RESULTS  In the part of movement observation ranged from 57% for close elongated pinch ( from the issue of exerted force)to 100% for elbow flexion, neck flexion,lateral rotation and etc.  For the part of posture observation, interrater agreement ranged from 83% for kneeling ( in the issue of accumulative time) to 100% for standing, awkward, standing with raising arm above shoulder and etc.

RESULTS  For all of the data, kappa calculation was not shown much different, ranged from fair to very good of both observation on movement and posture and seem to be similar when comparing within two observers as the first observer (A) was a standard

DISCUSSION AND CONCLUSION  The work observed in this study was fast- paced, and the workers combined several movement and postures into one continuous, fluid movement  gross body motion seem to be easier to observed and the result in better agreement than smaller motions  the extreme postures were much easier to noted when comparing with slight deviation from neutral.

DISCUSSION AND CONCLUSION . Well preparing of check list and selected each of all movement and postures( picture 1- 28) is so important  training all observers  needed furthur to evaluate in all issue of that movement and posture.

The real purpose  for safety officer of the industries( the well trained observers)  estimating risk factors and potential levels + interpreting the data of the self report musculoskeletal problems or diseases the adapted check list for movement and posture observation

The best ergonomic exposure assessment method ???  appropiateness for use in the large populations at reasonable cost  the versatility to estimate a variety of exposure factors  the ability to represent the exposure of the job over appropiate length of time  Reliabilty and validity of the method

interrater reliability of observation  operational definition simple and clear  long and multiple training sessions  number of observation  the level of detail  maybe longer observation periods and repeated observations.

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