In Chapter 4 we discussed basic principles of probability, and in Chapter 5 we presented the concept of a probability distribution. After completing this chapter, we will be able to solve problems in a wide variety of different disciplines, including ergonomics.ģ 250 Chapter 6 Normal Probability Distributions 6-1 Review and Preview In Chapter 2 we considered the distribution of data, and in Chapter 3 we considered some important measures of data sets, including measures of center and variation. This chapter introduces the statistical tools that are basic to good ergonomic design. (The mean weight of the 25 passengers aboard the boat that sank was found to be 168 lb.) The National Transportation and Safety Board suggested that the old estimated mean of 140 lb be updated to 174 lb, so the safe load of 3500 lb would now allow only 20 passengers instead of 25. Assuming a mean passenger weight of 140 lb, the boat was allowed to carry 25 passengers, but the mean of 140 lb was determined 44 years ago when people were not as heavy as they are today. An investigation revealed that the safe passenger load for the water taxi was 3500 lb. Among the 25 people on board, 5 died and 16 were injured. A water taxi sank in Baltimore s Inner Harbor. A subsequent investigation showed that most of the passengers weighed more than 200 lb, and the boat should have been certified for a much smaller number of passengers. Based on an assumed mean weight of 140 lb, the boat was certified to carry 50 people. Twenty passengers were killed when the Ethan Allen tour boat capsized on New York s Lake George. This prompted the Federal Aviation Administration to order airlines to collect weight information from randomly selected flights, so that the old assumptions about passenger weights could be updated. In the subsequent investigation, the weight of the passengers was suspected as a factor that contributed to the crash.
The crash of the Beech plane killed all of the 21 people on board. We have an emergency for Air Midwest fiftyfour eighty, said pilot Katie Leslie, just before her plane crashed in Charlotte, North Carolina. For example, the following real situations illustrate the difficulty in determining safe loads in aircraft and boats. Bad ergonomic design can result in uncomfortable, unsafe, or possibly fatal conditions. Good ergonomic design results in an environment that is safe, functional, efficient, and comfortable.
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Ergonomics is used in a wide variety of applications such as these: Design a doorway so that most people can walk through it without bending or hitting their head design a car so that the dashboard is within easy reach of most drivers design a screw bottle top so that most people have sufficient grip strength to open it design a manhole cover so that most workers can fit through it. 2 CHAPTER PROBLEM How do we design airplanes, boats, cars, and homes for safety and comfort? Ergonomics involves the study of people fitting into their environments.
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