Some slides based on a workshop I run on Project Planning and Estimating.
Transcript of Project Estimating
1. Project planning and estimating How long is a piece of
string?1 Copyright ISC 2012
2. Hofstadters Law Hofstadters Law states that, when planning
any task, it always takes longer than you expect, even when you
take into account Hofstadters Law In other words, projects over-
running are almost inevitable because of the way our brains think
about how long stuff takes to do Estimating tools can help you2
Copyright ISC 2012
3. Estimates and Estimating An estimate is an approximation of
project time and cost targets that is refined throughout the
project life cycle Estimating uses a range of tools and techniques
to produce estimates Copyright ISC 2012Estimating: 3
5. Bottom-up estimating Assumes that future costs for a product
can be predicted accurately from historical costs of that product
Uses detailed costs of components, built up into an end product
(WBS/PBS) e.g. 10,000 bricks, 250 tiles, 20 litres of paint = total
cost of xxx Also known as Detailed Estimate, Engineering Build-up,
or Grass Roots method Copyright ISC 2012Estimating: 5
6. Parametric estimating Collecting relevant historical data,
usually at an aggregated level of detail, and relating it to the
project to be estimated through the use of statistical techniques
At the heart of the parametric estimating methodology are cost
estimating relationships (CERs) e.g. 1 hour of filming will require
5 hours of editing e.g. 10% of the cost of developing a new website
is associated with User Testing Copyright ISC 2012Estimating:
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7. Comparative estimating Takes actual costs of similar
existing or past projects, and makes adjustments for complexity,
technical, or physical differences to derive the new project
estimate e.g. 10 new web pages took 3 weeks and 15k on project X,
so we estimate project Y requiring 20 new pages will take 5 weeks
and cost 25k Also known as Analogous Estimating Copyright ISC
2012Estimating: 7
8. Other estimating methods 3-point estimates Expert judgement
Come up with 3 numbers: Ask the project team and Realistic (most
likely) Subject Matter Experts Best case (optimistic) Worst case
(pessimistic) Estimate = (B + 4R + W)/6 N.B. the formula is usually
weighted (4 x R), but sometimes is the simple average of B, R &
W Copyright ISC 2012Estimating: 8
9. Example 3-point estimate ID Tas k Nam e Duration Optimis tic
Dur. Expected Dur. Pes sim is tic Dur. 1 Programm e plan 200 days
180 days 200 days 280 days 2 Office project 10 mons 9 m ons 10 mons
11 mons 3 New technology project 9.67 mons 8 m ons 9 m ons 14 mons
4 Project re staff 66.67 days 50 days 65 days 95 days 5 Com
munications 66.67 days 50 days 65 days 90 days 6 Group s taff types
1.17 wks 1 wk 1 wk 2 wks 7 Develop comms plan 2.33 wks 2 wks 2 wks
4 wks 8 Staff prepared 0 days 0 days 0 days 0 days 9 Com municate
intentions 9.83 wks 7 wks 10 wks 12 wks 10 Staff numbers 46.67 days
35 days 45 days 65 days 11 Set up database 1.17 wks 1 wk 1 wk 2 wks
12 Count s taff 5.17 wks 4 wks 5 wks 7 wks 13 Set up s urvey 2 wks
1 wk 2 wks 3 wks 14 Input data 2.17 wks 2 wks 2 wks 3 wks Estimate
= (O + 4E + P)/6 N.B. the formula is usually weighted (4 x E), but
sometimes is the simple average of O, E & P Copyright ISC
2012Estimating: 9
10. Test yourself: Which method does the project team use to
estimate costs of building a new e-learning course? Expert 3-
Compa- Para- Bottom- Point rative metric up The team identifies a
best, worst and most likely case and averages them The team asks
two suppliers who have built e-learning courses before The team
uses a spreadsheet of data from previous projects and it calculates
cost and time estimates for them Members of the team have been
involved in 4 previous e-learning projects and know exactly how
long each one took and what they cost Theres so much work to be
done that the team breaks the project down into 75 work packages
Copyright ISC 2012Estimating: 10
11. A final thought Quote from a clients Project Manager: We
try to fall behind as early as possible because that gives us
longer to catch up11 Copyright ISC 2012