Why is the modified fibonacci sequence used when estimating
Fibonacci Series = Accurate Agile Estimates? + FREE Cheat Sheet
does using the Fibonacci series for
estimating improve the accuracy of those
estimates that's the question we're
going to be looking at today and stick
around to the end to get your hands on
this free agile estimating cheat sheet
my name is Gary Strom welcome to
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along with this series on agile
estimating you'll have got the message
by now that estimating is hard but some
estimates are much easier than others
we've talked previously about estimates
of absolute size versus estimates of
relative size how heavy is this is a
hard question which of these is heavier
is an easy question why is it an easy
question well it's because there's a
large difference we assume in the white
of these two when I say difference is
that the absolute difference or the
relative difference which of these two
coins is heavier which of these two
bridges is heavier I hope that answers
the question
it's not the absolute difference that's
important it's the relative difference
hold on a second one there supposed to
be an episode on the Fibonacci series I
think it's time we rolled it in actually
let's build it from scratch the first
two numbers are 0 1 1 and to get the
third we add the first two together 0
plus 1 is 1 and we carry on adding pairs
of numbers 1 plus 1 gives us 2 1 plus 2
gives us 3
two plus three gives us five and so on
eight
13:21
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34 55 89 what's interesting in this
series is the gaps between the numbers
not the absolute gaps the relative gaps
the relative gap between these two is oh
that's infinite yeah that one's a little
bit large let's move on
the relative gap between these two is
100% okay 50%
66.6 recurring percent 60%
sixty two point five percent sixty one a
bit percent almost sixty two percent
sixty one point eight sixty one point
eight after some craziness at the
beginning of the series the relative gap
between the members of the series
settles down to around 60 Warren and a
bit percent let me see if I can
demonstrate that to you a little more
visually here are the first few 0 1 1 2
3 5 ah yeah now we're at space so I'm
gonna zoom out round about sixty percent
and there's the 8 zoom out another 60
percent
there's the 13 zoom out again 21 zoom
out once more
34 zoom out again 55 zoom out one last
time
89 I hope you can see that although the
bars are getting skinnier as we zoom
further and further out the relative
size between this one and this one stays
pretty well constant
the reason that the scale works so well
for estimating is that it encourages us
to stay in the realm of easy estimates
it encourages us to stay with relative
estimates to say in slightly different
terms if we are estimating two things
and their sizes their relative sizes are
not sufficiently different then we
consider that they both have the same
size which brings us right back to the
question that we started with today does
the Fibonacci series lead to more
accurate estimates I think the answer
has to be no if anything what it does is
protect us from attempting to make
accurate estimates it keeps us in the
realm of making rough or broad estimates
so I'm curious do you use the Fibonacci
series for your estimate I'd love to
know let me know in the comments below
and finally today there's the small
matter of the cheat sheet that I
mentioned at the beginning the agile
estimating cheat sheet you'll find a
link in the comments below click the
link follow the instructions and it's
all yours thank you very much for
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next time cheers for now
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