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"Planning & Estimating", the "Bonnie & Clyde" partnership of Project Management

There are many great partnerships in world history, Bonnie & Clyde, Batman & Robin, Lennon & McCartney Morecambe & Wise; the list is extensive. Planning & Estimating is the great partnership of Project Management and they need to work together to give you a credible plan.

Estimating focus of this post

I've already spoken of Planning in a previous post so Estimating is the focus of this post. 

Try not to be influenced by "plan expectations" when undertaking estimating, the classic "We really need to get this task done in 2 weeks - umm, yes I think this will be possible". Come with an open mind to the estimating process and be prepared to call out a large estimate as per this Proverb.

Project Estimation - Good estimators aren't modest - if its huge they say so

If possible estimate from different standpoints

I must admit to be a fan of bottom up estimating whenever possible. Decompose a task into lower level items which can be better estimated and then aggregate up.

But top down estimating can also be useful especially as a phase check. In IT waterfall software development projects, a classic approach is to perform a bottom up estimate on the likely construction effort and then "expand from construction" to give estimates for other phases using industry (or even better locally derived) effort percentages across phases such as:
  • Initiation 6%
  • Analysis 8%
  • Design 15%
  • Construction 25%
  • System & Integration Testing 28%
  • Acceptance Testing 12%
  • Implementation 3%
  • Post Implementation 3%
Project Estimation - Estimators do it in groups - Top Down and Bottom Up

From the Proverb above you can also gather that it is good to get several people involved in estimating rather than rely on 1 person. This is particularly important when asking an "expert". I prefer to have separate estimates prepared by a couple of experts rather than have two experts in the same room as I find that one will often defer to the other and you won't get the possible contrast.

Sometimes you may need to make assumptions in estimating. Please document and ideally close off as many as you can during your estimating phase. Every open assumption is a risk to be assessed.

Confidence in estimates

It is good to assess confidence as part of the estimating process, you may assess
  • have we done similar things before?
  • is this completely new to the organisation?
It is often beneficial to focus the team on coming up with a range of estimates (although this can increase the effort required):
  • pessimistic worst case estimate
  • optimistic best case estimate
  • realistic most likely case estimate

Some common mistakes

  • Politics - estimating to meet a project deadline / cost constraint
  • Lack of experienced people in the subject matter being estimated
  • Haste - cutting corners in your estimating because you are under pressure to deliver something
  • Estimating assuming an expert is doing and then asking the new recruit to undertake
  • Sand-bagging - over estimating for an easy life
  • Super-optimistic - assuming is it always going to go perfectly
  • Quality - forgetting to estimate for quality processes
  • Incorrect scope and/or work breakdown
  • Not writing down the rationale for the estimates, what is included and any assumptions

And Finally...

When you have done your estimating and reflect this back in the plan beware the temptation to add an unrealistic number of resources to achieve an end date as illustrated by the Proverb "It takes one woman nine months to have a baby, it cannot be done in one month by nine women"

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