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Human Factors Home
Ergonomics General Notes
This page provides a few general guidance notee relating to the information provided on this
site and its relevance to mechanical engineers
This website contains various values and dimension obtained from a variety of sources relating
to ergonomics or human factors - the relationship between man and machines. I have tried
to provide links which include better quality information and in the reference book section of this site
I have identified books which are useful. If the information you seek is important please
use these sources of information.
Engineers are responsible for the safety of those using the equipment they design, make or maintain and
and should reference the relevant regulations
It must be stressed that man comes in so many variations that it is not possible to
provide set values for sizes and strengths of men to be used for the design of equipment
and access spaces. A individual person starts as a child and ends as a old person
and within that period can be fat or thin, strong or weak, well or ill. Throughout the world
there is significant variation in the normal strength and sizes of individuals.
In designing equipment it is desirable that the majority of relevant indivuals should
be able to operate the controls and the equipment should be strong enough and large enough to withstand
and support the biggest, strongest and heaviest persons. Equipment should be specified
for the weakest,the strongest, smallest, the largest users.
When looking at a range of strengths and sizes individuals it is necessary to use
statistics. The individuals are assumed to be distributed in a normal distribution.
In a normal distribution all three statistics, the mean, median, and mode are the same.
The confidence interval of a normal distribution is the middle percentage of the total
population. A CI of 95% of a population excludes the bottom 2.5% and the top 2.5% of the collection.
The confidence interval of a population may be obtained from the mean and the SD using the following:
- Confidence interval 66% = Mean +/- 1.SD
- Confidence interval 90% = Mean +/- 1,65.SD
- Confidence interval 95% = Mean +/- 1,95.SD
In a population the mean = 50 and the SD = 5
Therefore 45-55 ( 50 +/- 5) include = 66% of the population.
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Last Updated 24/04/2008