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Table 10. Elements for determining the multiplier factor for effective items EI
Score of effective items 0 1-4 5-8
9-12 12
Multiplier factor 1 1.5 2 2.5 3
4.1. Applicability of the CEI
The proposed CEI model has been applied successfully in several studies performed by the author unpublished reports; this success shows that it can be
used in the study of many repetitive single or multiple tasks without any limitations. In most cases the aim of studies has been to identify and assess the risk factors of
UEMSDs and injuries for individual employees. A more detailed and general purpose was to assay, measure and investigate the reliability and validity of various
survey risk factors involving in calculating the CEI Score. The studies have been performed in different fields, including weaving and textile industries,
manufacturing industries, carpentry, steel industry, post offices, service industry, electronic industry, shopping and marketing, agriculture and farming industry,
tailoring and sewing, hair styling, baking, and bricklaying.
4.1. Applicability of the CEI
The proposed CEI model has been applied successfully in several studies performed by the author unpublished reports; this success shows that it can be
used in the study of many repetitive single or multiple tasks without any limitations. In most cases the aim of studies has been to identify and assess the risk factors of
UEMSDs and injuries for individual employees. A more detailed and general purpose was to assay, measure and investigate the reliability and validity of various
survey risk factors involving in calculating the
4.2. Reliability and validity tests of the CEI 4.2.1. Inter-observer reliability test of the assessment items
Inter-observer assessment reliability Table 11 was assessed to identify possible sources of error in the reliability assessment test process. In this test, 31 various tasks
were randomly selected from 31 different jobs involving manual handling tasks with varied part load weights. The ergonomic field study assessed static and
repetitive tasks; highly repetitive tasks; repetitive tasks with low, moderate and high force exertions; sedentary or standing tasks; and non- repetitive tasks with low,
moderate and high force exertions. Video-tape recordings were viewed in slow motion to confirm the assessment of the observer. Several pilot tests quantified that
assessment durations of 5-7 minutes are sufficient to complete the assessment
Chronic Exposure Index Model to Assess Ergonomic Risk Factor Related to Upper Extremity Musculoskeletal Disorders
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process by most observers. Twenty-five observers comprising of five general observers without any experience in ergonomic assessment tests, and 20
professional observers with 2, 4, 6 and 7-8 years’ experience in ergonomic assessment tests in ergonomics and occupational Health were selected randomly.
The mean age of observers was 39.8 years SD = 12.7, Range = 21-57. Excluding the five non-experienced observers, the average experience of observers was 4.9 years
SD = 3.2, Range = 2-8. The 25 observers were divided into five groups, and each observer in each group separately assessed the various tasks both in the field and
using video-tape-recordings.
As assessment work experience increased, inter-observer reliabilities both Cohen’s Kappa 35 and percentage agreement in assessing items used in
calculating the CEI score increased. According to the classification proposed by Landis and Koch 35, single and total percentage agreement for any item was 60
and all kappa factors for strength of agreement were 0.20 “Fair” to “almost perfect” agreement. Percentage agreement in most items were either close to or
60; this agreement can be considered “acceptable” 35, 36, 37.
Table11. Inter-observer reliability on assessment items as specified in the CEI
All observers 5 observers
with no experience
5 observers with 2 yrs’
experience 5 observers
with 4 yrs’ experience
5 observers with 6 yrs’
experience 5 observers
with 7-8 yrs’ experience
Assessment items
Kappa agree
ment Kappa
agree ment
Kappa agree
ment Kappa
agree ment
Kappa agree
ment Kappa
agree ment
Force exertion
0.46 80.1 0.36 76.1 0.39 77.4 0.43 79.5 0.46 79.9 0.56 83.6
Upper limb posture
0.45 82.5 0.29 71.3 0.31 81.6 0.36 83.3 0.54 85.2 0.68 86.5
Force frequency
0.47 68.6 0.33 61.5 0.41 63.6 0.43 67.2 0.48 69.4 0.52 74.2
Duration of force exertion
0.42 71.3 0.34 62.4 0.35 67.6 0.38 71.3 0.41 74.2 0.57 76.3
Task duration
0.35 70.1 0.28 63.8 0.31 67.6 0.35 69.6 0.37 70.1 0.43 72.9
Speed of force exertion
0.50 79.5 0.31 69.7 0.33 73.5 0.39 77.2 0.41 81.6 0.52 83.7
Parts weight 0.42 86.4 0.32 81.3 0.36 81.9 0.38 86.2 0.43 85.4 0.55 87.2
Lack of recovery
periods 0.47 75.8 0.27 63.7 0.30 76.2 0.34 73.5 0.66 78.6 0.69 81.8
Age factor
0.81 94.8 0.65 85.2 0.73 89.5 0.79 97.3 0.83 98.6 0.96 99.8
Effective items
0.39 67.4 0.32 63.1 0.34 63.5 0.38 66.7 0.39 68.4 0.45 73.5
