Design by rule of thumb
I am collecting all "rules of thumb" examples in engineering used to either design or give a design a quick sanity check. Could you please e-mail any that you use or know of to me. If you know the origin or explanation (maths) behind it, I would appreaciate it.
I think it is very interesting and have to date not yet found a database of these "quick short cuts", which is the result of years of experince in engineering.
A rule of thumb given to me for evaluating another person's estimate was
as follows. Divide 50 by the person's age. Multiple the results by the
estimate. Example. estimate 5 weeks, age 35, 50/35 = 1.43. Plan for an
effort of 5 x 1.43 = 7.1 weeks.(filter) You learn over time that stuff happens.
Sick time, phone calls, a customer is down & needs help
now....things than have nothing to do with the initial task but will
take time from it.
After age 50 (this assumes you have been doing
this type of job for a good portion of your working career) you know
about these things & have baked this into the estimate with little
thought. If a factor of less than one proves to be needed, the over 50
guy may not be accounting for productivity tools. Just a few years ago
we waited a week to get photos from staff in the field. Now we can have
photos in a few minutes & request more while the person is still on
the site. This turns 1-2 weeks into 1 day effort. Same is true with CAD
files vs mailing paper prints.
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