Tag Archives: estimation

Better Estimation – Looking Back To Look Forward

It should not be surprising that the best way to estimate how long something will take, is to understand how long it took last time. In many cases this data is not hard to find, even though the project might be new, many of the tasks within it are not.

So how do you do your estimates? Do you start with a blank page, or look back at your last project?

Managing Risk – Part 2

Risk involves some form of estimation, as Flyvberg has shown, the best estimates are based on past, factual reference data, but for most projects that’s hard to obtain and so project managers are left to rely on their estimation skills. There’s an exercise on estimation here that I think everyone should do at least once. Most people are over confident in many areas.

Do you think you are a better driver than average? 93% of people put themselves in that category (of course it should be 50%). The same is true of estimation, and it’s an area that’s key to risk management, the temptation is to be excessively precise in one’s estimates, and this level of false precision understates true risk.

source: Joe Futrelle

The Deepwater Horizon Disaster and Estimation Techniques

Effective estimation of time, money and other resources is key to effective project management. For that reason it’s interesting to look at best practises, and a hotly debated estimate for the past 2 months is how much oil is flowing from the Deepwater Horizon spill.

A Flow Rate Technical Group has been established to estimate this number and the approach there are taking is detailed here.

Basically, the panel of experts is splitting into sub-groups, using different methods. These estimates will then be combined into one overall estimate.

The methods they are using are:

  • Plume Modelling – looking at video of the oil escaping in the water
  • Mass Balancing – looking at satellite data of the volume of oil on the surface adjusting it for any oil that hasn’t reached or left the surface
  • Reservoir Modelling – analyzing the composition of the oil reservoir under the seabed and determining oil pressure and hence flow rate
  • Nodal Analysis – examining the leak points on the seabed and calculating flow based on that
  • Woods Hole Analysis – using acoustic technologies to collect data close to the leak source

This calculation of numerous estimates using independent techniques is best practise in estimation. As you produce estimates, explore different techniques to create independent estimates, the overall estimate is likely to be more robust as result.

Neutral Questions

It’s very easy to influence people’s answers based on the questions you ask. For example, if you ask a leading question such as… So you’ll have that report on South America finished by Friday, right? Then you’ll be much more likely to get a positive (and possibly misleading) response than if you ask something more balanced along the lines of… When will the report on South America be complete? Of course, there’s a big difference between getting the superficial answer you want and getting the true, underlying data you need to make an accurate estimate or decision.

The questions you ask determine whether you will get realistic information back or not. Be careful how you phrase them. Balanced questioning can be critical in spotting potential problems early.

If you want to take it to the next level, you could probe after the initial question. When’s the earliest you’d could ever produce the report, what would cause that to happen? When’s the latest you’d get the report, what would cause that to happen? That way you can move from a single point estimate to a range of outcomes, with the latter being more reflective of the real world.