Hitting Deadlines: Master the Art of Estimating Time
GOOD NEWS! You already subconsciously, naturally and without any formal
training, use a process very similar to a formula from Project
Management Science called Program Evaluation Review Technique or PERT.
In this article I will show how to estimate time much more accurately
using this tool. In the next article I will show you how to know how
confident you can be in your estimate.
You are planning a dinner party. You need to send out invitations. You choose to send e-invites instead of paper. Most of your friends will get back to you in about a week. A few will get back to you in a day or two. Some will take two weeks, and some won't reply at all. So you will need to send invitations out two weeks before the party. Just to make sure. Or do you?
Let's call the whole bunch of friends who will get back to you in a week TM for TIME MOST LIKELY
Let's call our friends who are flakes and will take two weeks TP for TIME PESSIMISTIC
Let's call the combination of all this our TE or TIME ESTIMATE.
After the following course announcement I will show you the standard formula from PERT for estimating time.
(TO + (4TM) + TP )/6 = TE
If we convert our estimates of when people reply to our invitations to days we now have the following information.
Time Optimistic is TO = 2
Time Most Likely is TM = 7
Time Pessimistic is TP = 14
Now we plug in the numbers:
(2 + (4x7) + 14)/6 = 7.33 days or ABOUT A WEEK! Not Two Weeks!
CAUTION! You are not yet ready to use this process with CONFIDENCE! There is a missing piece. To use this process well you have to know how likely it is that you will get enough invitations back by your estimate to finalize the details of the party.
In a future articleI will show you how to be confident that 94% of your invitations will be back between 3 and 11 days after you send them out.
And the formula to find this confidence will be easier than the one above.
TO is TIME OPTIMISTIC
TM IS TIME MOST LIKELY
TP IS TIME PESSIMISTIC
TE IS OUR TIME ESTIMATE
Practice this process and you will be well on your way to becoming a master at estimating time.
Many of us, by our very nature, and it is neither good nor bad, are either optimists or pessimists. This means that if we do not use a process like the one above we will be greatly over or greatly under our time estimates!