- Evaluation of Inter rater Reliability for Movemen

t and Posture Observati ons of workers in an Aud

io Compact Cassette Plant

Dararat Techakamolsuk Pornchai Sithisarankul

- INCIDENCE OF WORK RELATED MUSCULOSK

ELETAL DISORDERS : social security office, MinistryofLaborandsoci al wel f ar e 1 9 9 8

SEVERITY LIFTING HEAVY OBJECTS INJURIES/ ILLNESS FROM WORKINGIN THE SAME POSITION CONSTANTLY

DEATH 1 3

PERMANENTPARTIAL

DISABILITY

19 15

TEMPORARYDISABILITY ( MORE

THAN 3 DAYS

1,432 527

TEMPORARYDISABILITY( NOTMORE THAN 3

DAYS)

10,134 2,522

Ergonomics is defined as the study of the interactionbetween workers and the equipments being used and theenvironments in which they function

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 force3. Non –neutral position or postures4. awkward postures5. localized contact pressure6.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 METHODSSubjects - 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 2000in an audio compact cassette plant, area

of molding department , audio assembly area and audio package department

MATERIALS AND METHODSInstrumentThe 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 1- 17 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 18- 28 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…. Repet itionof pi c . 2

Observer A Very oftenObserverB

Often Occational TotalVery often 9 1 0 10

Often 2 9 1 12

Occational 0 1 4 5

Total 11 11 5 27

2227 08148 8Percent agreement = / = . ( % %148

%%%%%%%% %%%% %% %%%%%% % % %= 9 .44

11*10 27 407very often = ( ) / = . 12*11 27 444often = ( )/ = . = ( 5 * 5 )/ 2 7 = 0 .9 3 944 27 035proportion of the total . / = . - 081035 1calculate the agreement as ( . . ) / (

- 035 070. )= . = 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 0.21 - 0.40 Fair 0.41 - 0.60 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 kappaf ii is the number of agreements for

categories i : The expected proportion of agreements by chance is given by g

P e = i =1 rici / n2 The index of agreement, kappa, is

given byK= 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 - 1.96 Se(k ) to k + 1.96 Se(k )

RESULTSIn 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.

THANK YOU