Skip to main content

Estimation math made easy via zequals

How precise are your estimates?  Are we inferring false precision with those 5 significant digits?

I saw an hours estimate for a medium size project at our company just the other day.  I don't remember the actual digits, but that's not the point it was a number like:
4145.8 hours
Let's just assume that a team of 7 people will do this project.  How many weeks is this?  I'd guess 4145.8 hr divided by (7 * 40) equals 14.806 weeks.  Or, as a human would say it 15 weeks, give or take.

Are those digits really necessary?  No.  Are they even real?  No.  They are just artifacts of inappropriate rounding or truncation.   There is very little doubt that someone could estimate a 4000 hour project down to the quarter of an hour (the implied accuracy of the 0.8 hour).  And if you think they are so good at estimating that they can distinguish between 45 hours and 50 hours for a portion of this project - well, then keep on trucking to the minute, or second.  There is a problem with your math.

Your solution is EASY.


So here's a solution that makes the calculator obsolete - estimation is an art - learn to use it in your math.  Learn the power of ruthless rounding via the technique called zequals by Rob Eastaway.  Zequals is a math symbol much like the equals sign.  And means much the same thing.  What is on one side of an equation is zequals (or almost equal) to the other side of the equation.  The symbol is: (insert graphic here), but since I don't have one on my keyboard I'm going to use z= to represent zequals.  It is a method of approximating each term in the equation by it's rounded value to one significant digit and then performing the math.  An example right about now would be helpful.

7 * 8 = 56  but 7 * 8 z= 60.   Perhaps another example will help.

13 * 38 = 494 but 13 * 38 z= 10 * 40 z= 400.   Are you thinking this is not very accurate or precise?  Then look here on Periodic Videos for an error graphic. Now, let's try some bigger numbers.

456 * 378 = 172368  however 456 z= 500 and 378 z= 400 and 5*4 = 20 so add in the other zeros, that 4 more zeros and you get 20,0000.  Now do you see how easy zequal makes math of estimates?

Here watch Rob explain it, now that your interested.




Will you start doing your project estimation math using zequals?  I will.  Thanks Rob.  Here's his math book for moms and dads.

See Also:

Relearning to Count - Zero, One, Many


Post a Comment

Most Popular on Agile Complexification Inverter

Exercise:: Definition of Ready & Done

Assuming you are on a Scrum/Agile software development team, then one of the first 'working agreements' you have created with your team is a 'Definition of Done' - right?



Oh - you don't have a definition of what aspects a user story that is done will exhibit. Well then, you need to create a list of attributes of a done story. One way to do this would be to Google 'definition of done' ... here let me do that for you: http://tinyurl.com/3br9o6n. Then you could just use someone else's definition - there DONE!

But that would be cheating -- right? It is not the artifact - the list of done criteria, that is important for your team - it is the act of doing it for themselves, it is that shared understanding of having a debate over some of the gray areas that create a true working agreement. If some of the team believes that a story being done means that there can be no bugs found in the code - but some believe that there can be some minor issues - well, …

Elements of an Effective Scrum Task Board

What are the individual elements that make a Scrum task board effective for the team and the leadership of the team?  There are a few basic elements that are quite obvious when you have seen a few good Scrum boards... but there are some other elements that appear to elude even the most servant of leaders of Scrum teams.









In general I'm referring to a physical Scrum board.  Although software applications will replicated may of the elements of a good Scrum board there will be affordances that are not easily replicated.  And software applications offer features not easily implemented in the physical domain also.





Scrum Info Radiator Checklist (PDF) Basic Elements
Board Framework - columns and rows laid out in bold colors (blue tape works well)
Attributes:  space for the total number of stickies that will need to belong in each cell of the matrix;  lines that are not easy eroded, but are also easy to replace;  see Orientation.

Columns (or Rows) - labeled
    Stories
    To Do
    Work In P…

Webinar: Collaboration at Scale: Defining Done, Ready, and NO.

I was invited to participate in a Scrum Alliance Webinar.  Maybe you would like to listen to us in a discussion of techniques to collaborate at scale (remotely and with many people).  The topic is one that I've got some experience in discussions - yet I never seem to get to done...
Collaboration at Scale: Defining Done and Ready and NO for Distributed Teams
With Joel Bancroft-Connors, Agile Organizational Coach; David A. Koontz, Agile Transition Guide; and Luke Hohmann, CEO and Founder of Conteneo, Inc.


14 February 2018 11 a.m. ET (USA).




The Scrum Guide is pretty clear on the criticality of the definition of Done: "When a Product Backlog item or an Increment is described as "Done," everyone must understand what "Done" means. However, the Scrum Guide ALSO says that the definition of Done can "vary significantly per Scrum Team." This leads us to examine when and how the definition of Done should vary, how distributed teams should cr…

A T-Shaped 21st Century Knowledge Worker

Knowledge workers in the 21st Century must have many areas of deep knowledge, while also be capable of collaboration across multiple other domains with dissimilar T-shaped individuals.  This description of a person is a metaphor.  Compare it to the shape of the "I" in the classic saying there is no "I" in Team.


I first read about Scott Ambler's term "Generalizing Specialist" - but it's so hard to remember the proper order of the words... get it backwards and it has an inverted meaning... T-Shaped is easier to remember. 
A generalizing specialist is someone who:
Has one or more technical specialties (e.g. Java programming, Project Management, Database Administration, ...). Has at least a general knowledge of software development. Has at least a general knowledge of the business domain in which they work. Actively seeks to gain new skills in both their existing specialties as well as in other areas, including both technical and domain areas.  General…

A FAILURE to Communicate

I was working with a failing team some time ago.  I use "failing" to describe the outcome of the team - not the people on the team.  Are you OK with that description?



An issue arrose in the stand up - a team member that was to verify the quality of a procedure did so and reported that there were a few records that didn't match expectation in the data set.  Upon inquire the number of records not matching was over 2000.  Most people acknowledged immediately the exaggeration - I could tell by the laughter.  After about 10 minutes of discussing the details of the problem - it appeared the team had a handle on the specific situation.

I stopped the discussion and inquired if they could name the impediment.  One team member did a great job of describing the impediment as a _communication gap_.  Wonderful - I could work with that - the problem had a name and it didn't include anyones Proper Name.

"If the problem has a first name; we are going to have a problem."

I&#…