What does a 3-Point Estimate Give Me?

If someone asks you “How long will it take for you to drive home from the grocery store?” you could probably give a very accurate estimate, especially if you made that drive many times before.  If they ask you “How long will it take you to fix the facet?”, (and you don’t even know what’s wrong yet) could you give them a very accurate estimate, or would you rather make some assumptions and give a range of estimates?  “Uncertainty” should drive us to provide a range of estimates, especially if we are expected to commit to a completion time.

Does this above scenario apply to efforts you estimate for work?  If so, how do you come up with your commitments?

Go one step further – are you responsible for the execution of complex projects (with many tasks and people involved, some of whom you may not know)?  If so, how do get to a credible project plan, and then, how do you communicate and defend it?  My answer would be “By applying 3-point estimates for uncertain (i.e., risky) tasks and using a Schedule Risk Analysis (SRA) tool to analytically evaluate the confidence levels for various estimates.”

The first response I typically hear is “That sounds reasonable, but it seems complicated and hard to do!”.  I might even agree with the second part of that response if it wasn’t for a new software tool called Chrono™.  So, say that I’m right about this new tool – wouldn’t it be worth a try?

Here is what you do.  Create an Integrated Master Schedule (i.e., a schedule that links tasks together so that when tasks are completed the whole schedule automatically adjusts accordingly to show how you or your team is doing) and give all tasks you best single-point time estimates.  If you do this with Microsoft Project, you can use Chrono™.  That is where the typical planning process ends.  But let’s not end there.  Work with your team to come up with two more estimates (Best-Case and Worst-Case), but only for the “risky tasks”.  Then enter them using the Chrono™ Wizard and run the Simulation.  Boom! You did it!  Your Schedule Risk Analysis output chart is automatically generated within a few seconds and displayed in your Web Browser.  This is not that complicated if you have the right tool to help you!

You might be wondering what the “risky tasks” typically are.  The usual culprits are listed below:

• Design Activities and Research
• System Integration
  • Merging of Multiple Technologies (i.e., Mechanics, Electronics, Software, etc.)
  • Integrating Components and/or Sub-Systems for the first time
• Test Activities
  • Early Validation Testing – to ensure basic product performance is achieved
  • Qualification Testing – to demonstrate functionality to customers, etc.
  • Long Term Reliability Testing
• Approvals or Authorizations to Proceed – from Inspectors, Sponsors, Customers, etc.
• Design-Build-Test Cycles or Iterations – e.g., making plastic parts from molds
• Out-Door Work Influenced by Weather
• Out-Sourced Activities and Critical External Resources
  • Critical Parts from Suppliers
  • Subject Matter Expertise via a Consulting Contract
  • Fabrication or Test Facilities by Test Services Companies

Here on some hints for how to get Best-Case and Worst-Case task duration estimates:

• Best-Case Estimates: Ask the person (i.e., the Subject Matter Expert) leading or performing the task “If everything were to go perfectly, what would be your estimate of the time (work-time) to complete the task?” – then use that number for the Best-Case estimate.
• Worst-Case Estimates: Ask the person leading or performing the task “What are the typical issues that can cause you to take more time, and what would be the total time (work-time) needed, including the estimated additional time to ensure that these issues are resolved?” – then use that number for the Worst-Case estimate.