A Simple Critical Path (PERT) Analysis for Time Estimation of Writing Projects

Time estimation is one of the critical tasks in any technical communication project.

How long will a project take? When will you start doing it?

And when do you expect to finish it?

Similar time-performance related questions are usually not easy to answer with 100% precision due to the number of variables that are usually beyond a writer’s control.

PERT for Time Estimation

But here is a simple critical path analysis (also known as PERT — Program Evaluation and Review Technique) that you many try to arrive at a rough estimate of your project’s expected duration.

Remind you, this is not the full PERT method but only a simple introduction to it.

PERT is a powerful statistical tool used in complex projects (like construction or engineering) with dozens or sometimes thousands of individual steps. But this much-simplified version should still help you if you have no way to calculate a time estimate for your technical writing project.

Here are the critical concepts (see the great article in Wikipedia):

• Optimistic time (O): the minimum possible time required to accomplish a task, assuming everything proceeds better than is normally expected

• Pessimistic time (P): the maximum possible time required to accomplish a task, assuming everything goes wrong (but excluding major catastrophes).

• Most likely time (M): the best estimate of the time required to accomplish a task, assuming everything proceeds as normal.

• Expected time (TE): the best estimate of the time required to accomplish a task, accounting for the fact that things don’t always proceed as normal (the implication being that the expected time is the average time the task would require if the task were repeated on a number of occasions over an extended period of time).

TE = (O + 4M + P) ÷ 6

Time Estimation Example

You say to yourself, “if I can finish this document in 6 days that would be a miracle!”. Your optimistic time (O) is 6.
Then you think: “If such and such factors are not there, my God, this project can take as long as a whole month.” Your pessimistic time (P) is 30.

But on the basis of your past experience with documents like this and also knowing the way your team (Client, Managers, and/or SMEs) respond to your review requests, you know that the job will probably take 14 days. You really think that’s the most likely outcome although you’d love it to finish in 6 days and you’re afraid that it may stretch out to 30.

This means your most likely time (M) is 14.

So your expected time TE is = (6 + (4×14) + 30) / 6 which yields (6 + 56 + 30) / 6 = 92/6, or 15.3 days.
Now you can tell your client or manager with some assurance that the documentation project will “more likely than not” take about 15.3 days.

And if they ask you how you arrived at that estimate, you can earn extra credit by telling them that you’ve applied PERT analysis to your raw time estimates.