LaVerne L. Hoag

The Effect of Inspector Accuracy on the Type I and Type II Errors of Common Sampling Techniques

The single sample and sequential sampling models are presented in a form which includes inspector error. The effect of inspector errors on the probability of type I and type II errors is discussed...

HUMAN FACTORS IN URBAN TRANSPORTATION SYSTEMS

Urban growth and the development of the megalopolis have forced a re-examination of all urban transportation systems in terms of their ability to satisfy human needs and preferences. Encouraging the re-emergence of public transportation in cities requires a total assessment of the physical and behavioral characteristics of the user population as well as their economic, social, and esthetic preferences. This population includes many groups not normally considered in human engineering design, such as the physically or functionally handicapped and the aged. Existing data am reviewed and research needs are identified for the design of urban transportation systems.

Strategies for Improving Visual Inspection Performance

This paper summarizes recent results obtained in inspection studies including several studies performed by the authors. Both static and dynamic visual inspection tasks are included. Based on these results, a proposed new integrated design procedure for inspection tasks that will approach the optimal design has been formulated. The review of recent research results includes the following primary variables: the speed of the item passing the inspector, the spacing of items, the percentage of defective items, the illumination level, the contrast between the item being inspected and the background, and the effectiveness of individual versus group inspection. The authors have used their research results in combination with the results in the literature to formulate new integrated procedures for designing inspection stations and job procedures. The authors have also analyzed the effects of inspector performance on the overall quality control plans already in use in industry. The economic effects of changes in inspector performance which result from redesign of the inspection task are then demonstrated as a part of the overall design procedure.

Anthropometric and Strength Data in Tool Design

With the increasing number of women entering jobs that have been traditionally classified as male jobs, there has developed an awareness that tools and equipment used on these jobs are not adequate for the characteristics of the female population. Using adjusted male data is difficult, because the strength of women compared to men is a function of the particular strength measurement being compared (Lauback, 1976). Snook (1974) has illustrated that the women working on industrial jobs involving lifting are significantly stronger than women who do not work outside of their homes.

Adaptive Effects of Static Muscular Strength Training

The trend towards mechanization of tasks involving manual labor has increased the importance of static muscular activity (isometric contractions). Information about the physiological reaction to static muscular activity has been increasing rapidly over the last few decades, but little information has been developed on the adaptive responses to chronic exposure to static muscular activity. This paper reports the results of an experiment on adaptive cardiovascular changes to a five week training program in which the % MVC was maintained at 50% for the entire program, i.e., weekly adjustments were made for increases in strength. The only significant change in the cardiovascular response to the training program was an increase in the rate at which the heart rate increased during periods of contraction. The average level of heart rate, systolic blood pressure and diastolic blood pressure did not change with training. Neither the systolic or diastolic blood pressure modified their rates of change due to training. Significant changes in strength and endurance hold capacity were also noted.

An Analysis of First Impression in the Reading of Electrical Schematic Diagrams

The initial impression of electronic troubleshooters of schematic diagrams was studied in a series of two experiments. In one experiment the time available to the subjects to view the information was restricted to 12 seconds and in the second experiment the subjects could look at the material as often and as long as they wished. The characteristics of the first element redrawn were: (1) the same elements were consistently selected, (2) the element was chunked with other elements, (3) the element was in a branch instead of a loop, (4) the element was along the exterior of the element and (5) the element was active more often than would be expected from the number of active elements in the circuit.

Human Factors Design Problems of Fire Fighters

Problems of job and equipment design that contribute to the occupational health and safety of fire fighters is reviewed. The job of fighting fires is physically demanding and most fire fighters do not have a fitness level to minimize the stress. The equipment used by the fire fighters needs to be redesigned to reduce the job related stress.

A Human Factors Evaluation of the American Kitchen

Kitchen design is evaluated using counter space, counter location and counter height as the criteria. A survey of apartment kitchens showed that designers generally follow the guidelines for total counter space, but the allocation of counter space to the different work centers makes the designs inadequate. An experimental study shows that the standard 36 high counter surface is not at the correct height for many kitchen tasks and a simple, economical design for adjustable cabinets is presented.

Response Surface Methodology and Optimization — A Possible Pitfall

Recently Response Surface Methodology (RSM) has come to the attention of researchers in the area of human performance, as evidenced by a special issue of Human Factors (August 1973) devoted to the topic. These articles, as well as others in the area, neglect to discuss the fact that RSM can be used as an optimum seeking technique. There can be, however, a serious practical problem or question that may arise in using the optimization technique associated with RSM (Cochran 1973). Those coefficients of the full model found to be insignificant can be eliminated and a new, or ~bbreviated, model determined with only the significant coefficients retained. The optimization procedure may now be applied, using either the full or the abbreviated model with the possibility of completely different outcomes. Considerable differences between the values of the independent and dependent variables may be found at the optimum points between the full and various abbreviated models.

PSYCHOLOGICAL DESIGN FACTORS IN URBAN PUBLIC TRANSPORTATION VEHICLES

Urban growth, pollution, and fuel shortages among other factors are causing the United States to place increased reliance on public transportation systems to meet daily travel requirements. Recent trends in transportation have shown a reluctance to accept public transportation as a viable alternative to the automobile. Even some advanced systems such as BART have not been well received. A major source of this reluctance has been attributed to the failure to successfully meet the psychological needs and preferences of the traveler in designing passenger compartments of public vehicles. A discussion is presented on important psychological variables such as personal space, situation control, esthetics, perceived safety, privacy, and forced interaction with other travelers. Recommendations are given for improving the design of urban public transportation vehicles.