Ergonomics. Exercises 9–16 involve applications to ergonomics,...

Question

Ergonomics. Exercises 9–16 involve applications to ergonomics, as described in the Chapter Problem.

Doorway Height The Boeing 757-200 ER airliner carries 200 passengers and has doors with a height of 72 in. Heights of men are normally distributed with a mean of 68.6 in. and a standard deviation of 2.8 in. (based on Data Set 1 “Body Data” in Appendix B).

d. When considering the comfort and safety of passengers, why are women ignored in this case?

Accepted Answer

All right. Hello, everyone. So this question says public buses are being redesigned to improve comfort for the majority of passengers. The seats have a fixed leg room of 32 inches. The leg length of adult passengers is normally distributed with a mean of 29 inches and a standard deviation of 3 inches. In the context of designing for public transportation, which of the following explains why taller passengers are not specifically addressed. And here we have 4 different entry choices labeled A through D. That we'll discuss individually later on. Starting off with option A, which reads that taller passengers are generally expected to stand during short or crowded journeys. So the fixed legroom in seat design is not prioritized for their comfort as they are less likely to be seated. This is incorrect, right, because it's not appropriate to assume that certain passengers based on their height are simply going to stay standing. And avoid seating altogether. When it comes to designing public transportation, the aim is to accommodate as many people as possible. Or as many people as reasonably possible. Especially for purposes of safety and accessibility. So ignoring taller passengers entirely is not justifiable. Option B on the other hand, says the design process focuses only on the average leg length, so passengers with longer legs will automatically have enough space since they are close to the average. This is not true. Right, and in order to understand why that's not the case, recall a few things about the normal distribution. Taller passengers are not closer to the average. Instead, by definition, taller passengers are closer to the upper tail of the normal distribution. Now, specifically, designing for the mean doesn't guarantee comfort for those above the average. So enter choice B is falsely assuming that designing designing for the mean covers everyone. Moving on to option C, it says that by ensuring the seats have enough legroom for the average adult passenger, designers inherently accommodate most taller passengers as well, due to the variability in leg length distribution. Now, to understand if this answer choice is correct or not, we have to understand how many standard deviations above the mean a leg length of 32 is. So to find that We find the Z value. And Z in this case is equal to. The value itself or capital X subtracted by the mean mu and divided by the standard deviation. So that's 32, subtracted by 29, and divided by 3, which ultimately equals 1. So what that means to say is that the leg length of 32 inches is one standard deviation above the mean, which means that approximately 84% of the population will find the leg room adequate for their needs. So therefore, right. Answer choice C is correct because it identifies the fact that designing for the average and slightly above the average inherently accommodates the majority of passengers. Including taller ones. But for the sake of completeness, option D, the multiple choice, says seats in public buses are typically adjustable in terms of length, or excuse me, in terms of height or backrest angle, but not in legroom space. So taller passengers are not the main focus when determining legroom design. This is not true. Not only because we already know that answer C is the correct answer, but also because wall height is adjustable in some vehicles, legroom is constant, especially in public buses. But whether or not the seats themselves are adjustable doesn't explain why taller passengers aren't specifically being addressed. It doesn't answer the question properly, is the main point here. So that's why, as mentioned before, the correct answer is option C in the multiple choice. And there you have it. So with that being said, thank you so very much for watching and I hope you found this helpful.

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Key Concepts

Normal Distribution

Mean and Standard Deviation

Ergonomics and Gender Considerations

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