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Why projects take longer than you think
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T3sl4co1l:
Related -- specific to software, but reasonably generalizable in most fields:
https://stevemcconnell.com/articles/software-quality-at-top-speed/

Tim
coppice:

--- Quote from: T3sl4co1l on April 16, 2019, 08:52:31 pm ---Related -- specific to software, but reasonably generalizable in most fields:
https://stevemcconnell.com/articles/software-quality-at-top-speed/

Tim

--- End quote ---
If you compared that with a hardware development activity you would find the benefits of early problem detection have a much greater impact than with software, but in most other respects the picture is pretty much the same. If you are looking at chip design, the cost and time benefits of early problem detection often become really extreme.
T3sl4co1l:

--- Quote from: coppice on April 16, 2019, 08:43:02 pm ---This sounds very plausible, but it usually dead wrong. Most hidden unknowns are still hidden when you break things down. When a reasonably cautious person makes a gut feel estimate they tend to factor in a more general estimate for how many things typically go wrong on other projects of comparable size. This has a better chance of making a reasonable allowance for things going wrong.

--- End quote ---

It's very easy to overlook things, even when they are knowable.  A lengthy itemized list looks comprehensive, but you can't spot what's not there...

Immediate example, I'm currently doing a little project that I quoted for two weeks design time.  The major oversight was package size: I failed to note that I wrote a fairly high power level into the spec, which wouldn't have fit the customer's mechanicals with the original intended design.  Consequently, I had to redesign the power section to take up less space.  This not quite doubled the design time -- just using up the time I quoted for that stage.

This is otherwise a very ordinary project, very similar to things I've done before, so I felt confident in quoting as I did, and the project is still on schedule.

If it were a more speculative project, I'd want to perhaps quadruple the design or testing time (or both), to allow for challenges in correcting and tuning the design.  A second round of prototypes may be recommended, too.

These are, of course, difficult things to sell a customer.  That's the biggest reason to keep current with components, literature, technology and practice, and equally so, reason to charge fair rates which cover all the education and research that feeds into your process.

Tim
NivagSwerdna:
If you can estimate accurately then you have probably misunderstood the problem... that's why Agile development is trendy... it is a recognition that we don't understand the problem.

PS
I'm just finishing up a two week project... it's taken me three months.  :-DD
T3sl4co1l:

--- Quote from: coppice on April 16, 2019, 09:05:23 pm ---
--- Quote from: T3sl4co1l on April 16, 2019, 08:52:31 pm ---Related -- specific to software, but reasonably generalizable in most fields:
https://stevemcconnell.com/articles/software-quality-at-top-speed/

Tim

--- End quote ---
If you compared that with a hardware development activity you would find the benefits of early problem detection have a much greater impact than with software, but in most other respects the picture is pretty much the same. If you are looking at chip design, the cost and time benefits of early problem detection often become really extreme.

--- End quote ---

Indeed -- it's one thing to have just labor costs, it's another to have material costs in addition to that labor.

This is a huge driver behind simulators: when total cost can be reduced by exchanging some materials cost, or risk, with labor costs.

(I guess, since PCB-level circuit simulation has languished over the last three decades or so, that's proof of which side of the balance that's on...)

Tim
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