Are We There Yet? Using Circles To Measure Progress

There's an old saying (with variations) that says:

"the first 50 percent of a project takes 90 percent of the time and effort;
The remaining 50 percent of the project takes the other 90 percent of the time and effort."

A similarly pessimistic sentiment about project estimation says:

"It always takes longer than you expect - even when you take into account the fact that it will take longer than you expect"

(source anyone? Mythical Man Month?)

You can't use a straight line to plot progress. Instead we make a lot of progress at first. And by the end progress slows to a crawl. But it isn't asymptotic to completion -- completion is eventually achieved.

I tried the simplest equation I know of that has this property -- a circle. (Well a quarter of a circle, to be precise)...

How far through do you feel you are? How far through are you really?

ActualProgress = Sqrt( 100^2 - (100 - ApparentProgress)^2 )

How To Read The Above Chart

When I think I'm half way there -- I'm not even 20% of the way there.

When I think I'm 99.5% of the way there -- sorry but that last half of a percent takes ten percent of the total time.

When I feel like I'm 87% of the way there --- I'm really only half way there.

When I feel like I'm 90% of the way there --- I'm not even 60% of the way there.

Anyway -- this was all just an exercise in dodgy-hand-waving-mathematics, but I like it. Don't use this formula for drawing up a billion-dollar-space-shuttle-budget, or anything like that.

'galloglass' on Thu, 19 Apr 2007 05:06:56 GMT, sez:

Try Hofstadter's Law:
http://en.wikipedia.org/wiki/Hofstadter%27s_law

'lb' on Thu, 19 Apr 2007 05:08:26 GMT, sez:

Of course! The recursive nature of the law should've given it away. That Hofmeister loves his recursion.

'blah' on Thu, 19 Apr 2007 09:14:48 GMT, sez:

At my company, we stop at 80% and then take a fraction of the remaining time to persuade our client he doesn't need the 20% more.
Very efficient method, I recommend it.

'chk' on Thu, 19 Apr 2007 11:31:03 GMT, sez:

Alternative: sqrt(x), x=0..1

This would even allow for extra features in the project if the time goes past finishing of the version (x > 1), while for the circle the progress goes backward.

Ch.

'Ryan Smith' on Thu, 19 Apr 2007 17:12:28 GMT, sez:

I thought it was:
"The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.""

I think that blah is onto something there. Just convince the client they don't need the last 20%.

'Carl' on Fri, 20 Apr 2007 13:16:34 GMT, sez:

Is it not more like an outward spiral?

If you start from the centre with a circle of a certain diameter to fill:

When you first start spiralling out from the centre, you are filling up your circle pretty quickly.

But as time goes on, you have to travel further and further around just to progress a slight amount further outwards.

The only benefit (maybe) is that it's a lot less dizzying near the end than it would be at the outset.

I have a feeling that I am fully Friday'd up, so I apologise for this waffle..

Have a good weekend all.

C

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