a-Fen Chi

Fatal occupational injuries in Taiwan — Relationship between fatality rate and age

Accident reports from the 1230 work-related single fatalities in the years 1989, 1990, and 1992 were collected and analyzed to reveal the significant factors contributing to such fatalities. The aggregated and disaggregated fatality rates of twelve accident types were standardized using the total number of workers of the same age, gender, and industry. The standardized fatality rates were subjected to the analysis of variance using age, gender, industry, workers experience, source of injury, and size of the company as the independent variables. It was discovered that industry and age were the main significant factors, and the interaction effect between industry and age was significant for the fatality rates of almost all accident types. The relationship between age and mean fatality rate differed depending upon the industry and accident type. Fatality rate has a significant rising trend with age for falls, collapse, being struck by and against, falling objects, explosion, drowning, and slipping and tripping accidents. Fatality rate of electric shock declined significantly with age.

A STUDY ON JOB PLACEMENT FOR HANDICAPPED WORKERS USING JOB ANALYSIS DATA

Abstract The current study determined job titles which can be adequately performed by various types of disabled workers. These job titles were chosen based on their loading scores on a number of critical job elements derived from a factor analysis on job analysis data. The sample of jobs consisted of 1285 occupations from the Employment and Vocational Training Administration which were summarized into 112 job titles. For each job title, 41 specific variables, falling in three major classes (required education and experience, physical demands, task environment) were factor analyzed, using principal components analysis with Varimax rotation. The five-factor (occupational hazard, verbal communication education and training, visual acuity, body agility, and manual ability) solution explained 58.4% of the variance. Applying the hierarchical clustering procedure to the loading scores on the five job factors, the 112 job titles were classified into 15 homogeneous clusters. By mapping the loading scores on the five job factors and the handicap profile developed [Bragman, R., Cole, J.C., 1984], job titles which can be adequately performed by the visually impaired, wheelchair dependent, learning disabled, mental retarded, hearing impaired and individuals with emotional disturbance can be classified. The results can be utilized by the Employment and Vocational Training Administration to expand both the counselor and counselees perspectives about job possibilities and job requirements. Relevance to industry A classification scheme of job titles was proposed for screening job titles which can be adequately performed by various types of disabled workers. The results can help to expand the perspectives about job possibilities and job requirements for handicapped workers.

Applying image descriptors to the assessment of legibility in Chinese characters

The current study derived seven descriptors from the pixel matrix of 5401 Chinese characters in the commonly used Ming, Kai, Li, and Hei fonts. A factor analysis was used to reduce the number of descriptors for a validation experiment. The three-factor solution (number of strokes, character height, and character width) explaining 89.54% of the variance was derived from 5401 characters in four fonts. A 4 x 2 x 2 x 2 factorial experiment using fonts, number of strokes, character height, and character width as the independent variables was conducted to evaluate the impact of each critical factor on the legibility of Chinese characters. Each tested character was chosen from the 500 most commonly used characters to minimize the effect of familiarity and ensure that all participants could recognize the character if it was legible. The 16 university students who participated in the experiment were asked to identify a Chinese character initially displayed on a PC screen at its minimum size and enlarged gradually until the participant could recognize it. The analysis of variance suggests that all the main effects of font, number of strokes, character height, and character width are significant. The legibility thresholds of the four type styles from the most to the least legible are in the Hei, Ming, Kai, and Li sequence. Number of strokes is the only significant factor in predicting the legibility threshold for each individual font. However, if predicting the legibility threshold across four fonts, character height is the other significant factor with about the same predictive power as number of strokes. The legible threshold is increased by the number of strokes and decreased by the character height and character width.

Do people choose an optimal response criterion in an inspection task

In order to provide models of human behavior useful in selecting tradeoffs in function allocation of inspection systems, an experiment was performed to test five optimization models of the decision component of inspection tasks. Ten subjects examined numbers printed on computer-generated Integrated Circuit (IC) chips to decide whether to accept or reject the ICs under different conditions of defective rate and payoff. The best fitting model was a form of the Expected Utility model, modified to account for the sluggish beta phenomenon. There was a significant relationship between subjects classified as Accurate on the Matching Familiar Figures Test and subjects best fitted by the modified Expected Utility model.

REANALYZING OCCUPATIONAL FATALITY INJURIES IN TAIWAN WITH A MODEL FREE APPROACH

This research reanalyzed 1230 work-related single fatalities from the years 1989, 1990, and 1992 with a model free approach. Each single fatality was analyzed in terms of the victims age, gender, industry, and the accident type. The standardized mortality ratio (SMR) was calculated to compare the SMR among various demographic groups and to cross validate the results obtained from our previous work using analysis of variance (ANOVA). The Chi-square Automatic Interaction Detector (CHAID) was used to divide the working population into segments based on whether the worker was a victim in any fatality. Predictor variables mainly focus on the demographic variables including the victims age, gender and industry. But different from our previous finding [Safety Science 27 (1997) 1] of an insignificant gender effect, gender was found to be the second critical factor and it was nested under the most critical variable, type of industry. Age is the least critical variable and it is nested under the gender effect. Five different interactive patterns were identified correlating the age, gender, and industries of the victims. A comparison among ANOVA, SMR and CHAID proved that CHAID outperforms other methods for it not only reveals the complex and hierarchical interactive patterns but also prioritizes the importance of the predictor variables.

Graphical fault tree analysis for fatal falls in the construction industry

The current study applied a fault tree analysis to represent the causal relationships among events and causes that contributed to fatal falls in the construction industry. Four hundred and eleven work-related fatalities in the Taiwanese construction industry were analyzed in terms of age, gender, experience, falling site, falling height, company size, and the causes for each fatality. Given that most fatal accidents involve multiple events, the current study coded up to a maximum of three causes for each fall fatality. After the Boolean algebra and minimal cut set analyses, accident causes associated with each falling site can be presented as a fault tree to provide an overview of the basic causes, which could trigger fall fatalities in the construction industry. Graphical icons were designed for each falling site along with the associated accident causes to illustrate the fault tree in a graphical manner. A graphical fault tree can improve inter-disciplinary discussion of risk management and the communication of accident causation to first line supervisors.

A new method for describing search patterns and quantifying visual load using eye movement data

Many methods have been used to describe human visual search patterns using eye movement data. However, none of them have considered fixation time and frequency distribution simultaneously, thus generating potential distortions in their resulting patterns. Therefore, a new method truly reflecting the search area covered by a subject is proposed. This methodology, named Weighted Search Area(WSA), describes visual fixations by vectors on a presumed X-Y coordinate system, then assigns a weight to each vector by its respective fixation time. Through various procedures of summing vectors and rotating axes, the Weighted Search Area and overall fixation vector can be calculated. WSA proved to be effective for comparing eye movement data collected under different driving environments. This methodology can be used as a quantitative measure for visual load where a large amount of visual attention is necessary. Relevance to industryA new method for quantifying overall visual load is presented and applied to the visual search patterns of a simulated driving task. The results are useful for the man-machine system interface design of visual display terminals tasks, control and display designs, driver behavior, instrument panel layouts, etc.

Matching performance of vehicle icons in graphical and textual formats.

The current research classified 82 vehicle icons into seven categories (image-related, concept-related, semi-abstract, arbitrary, abbreviation, word, and combined) for their matching accuracy, matching sequence, and matching time. These data can be compared and used as a framework for future icon development. Forty participants, all with a university degree, took part in this experiment. Half of the participants had intensive driving experience, while the other half never driven a car. The results indicated that on average, word icons had a significantly greater matching accuracy than the other icon formats; ranging from 4.7 to 20.8% difference. Regarding the matching sequence, participants matched image-related icons before other icon formats. Arbitrary and combined icons took significantly longer to match than other icon formats by 1.4-6.2 s. Based on the high matching accuracy (86.3%) and high ratings on subjective design features, word format can be used for functions describable using simple English for users with English reading ability. Confusion matrices showed that 63.2% of the misunderstandings were caused by similarity in format or function.

Measurement of information processing load and visual load on a dynamic information processing task

A dynamic visual information processing task was designed to investigate time-based and intensity-based factors on an operators information processing load as measured by reaction time, pupil diameter, and eye movement parameters. The time-based factor was manipulated by the target rate and scanning rate while the intensity-based factor was manipulated by the difference between a simple reaction task and a physical matching (choice reaction) task. Nine participants tracked the scanning line at two different scanning rates and were required to respond to two designated targets presented singly at two different temporal frequencies. The results indicated that task difficulty (the intensity-based factor) had a significant effect on the reaction time. Target rate and scanning rate were integrated as one time-based factor in terms of three sweeping angles. The time-based factor was found to have a significant effect on the fixation time, saccade amplitude, fixation frequency, eye movement speed, reaction time and hit rate. No interaction effect was found between time-based and intensity-based factors. The time pressure (defined by the time required divided by the time available) based on a model human processor was positively related to scanning rate, target rate and task difficulty. It was found to be the most objective and reliable if time required can be reliably predicted based on a predictive model approach.

Cross validation of measures of handle/human fit

The problem of measurement of effectiveness of handle design was addressed directly by scales. Ratings on several subjective scales were used and compared with maximum force exertion capabilities and grip force efficiency. Three of the handles were selected by overall preference ranking and tested using the Point of Subjective Equality (PSE) measure proposed by Hsia and Drury (1986). Factor analysis revealed two orthogonal factors, one related to overall preference and one related to strength. The PSE measure failed to give significant results.