Project Management

Manage project time requirements with these methods

If you're trying to get a handle on project time requirements, these project management methods will put you in a better position to come away with a plan that you can explain and execute.

One of the most common questions I hear from project managers is: How do I determine how long a project should take?

Many project managers use the old-fashioned gut check method, in which they rely on past experiences to guess how long it will take to complete a task. While this method may occasionally work for smaller projects, it becomes more difficult to accurately execute as the project grows in size and complexity.

The following methods can guide you in determining your project schedules with a higher degree of accuracy and help your organization efficiently plan and track projects.

Activity definition

Activity definition is when you break down a project into the individual tasks that are necessary to produce the project's deliverables. By using methods such as Organizational Process Assets, Enterprise Environmental Factors, Work Breakdown Structure, and the Project Scope statement in your project management plan, you can start defining the required activities.

There are many ways to go about this, but I tend to use process decomposition; it allows me to break down each element of the work packages into a scheduled activity by team member based on who is responsible for the package. At this point, you can also create the activity lists, which help define what needs to be done later.

Activity sequencing

Activity sequencing is when you decide the order in which the project's activities need to be completed. Two common methods for doing activity sequencing are the Arrow Diagramming Method and the Precedence Diagramming Method. I find the Precedence Diagramming Method more flexible for my projects, but I recommend that you assess the pros and cons of both methods to see which one works best for your projects.

Activity duration estimation

Many factors contribute to determining a project's activity duration; these factors may include business needs or situations that have legal requirements.

To estimate an activity's duration, start by using your Project Scope statement in order to understand any project constraints or assumptions that could impact your estimating. You can base your estimates on similar activities that have occurred in the past (analogous estimating), or you can estimate based on how long something typically takes to accomplish (parametric estimating). An example of a parametric estimate is: If it takes two weeks to build one house, it will take six weeks to build three houses.

You can also estimate an activity's duration by using the Program Evaluation and Review Technique (PERT) formula. PERT weighs the average of the pessimistic (P), most likely (M), and optimistic (O) estimates for an activity. For example:

PERT formula = (P+4M+O) / 6

Activity resource estimating

Once you know which tasks to complete, it's time to figure out: how many resources you need, when you need the resources during the project, and how long you will need the resources.

You shouldn't need to do much guessing because you can rely upon your Organizational Process Assets, expert judgment, published existing data, or bottom-up estimating when validating your resource requirements. All of these methods are valid ways to put firm numbers in place when determining your resource needs.

Schedule development

During schedule development, you bring together information from activity sequencing, activity duration estimation, and activity resource estimating to help build your project schedule, as well as your project schedule baseline.

If there are any issues at this point in your schedule, you can perform resource leveling or schedule compression. Resource leveling will help you manage your resources during periods where you may have initially found them to be over/under committed. Schedule compression will show you the impact of adding more resources to any critical path items or how running tasks in parallel can benefit the schedule.

Schedule control

While schedule control is part of the necessary Integrated Change Control process, you must also know where your project is at any point in time. This step will help you define and communicate how to handle things that affect the project's timelines. Any changes that may impact areas such as the schedule baseline or approved change requests need to be handled via this process to ensure you can track their significance on the project.

Summary

During the course of any project, you will struggle with questions about what to do and when to do it. By taking a more structured approach when defining and answering your questions about time management, you will put yourself in a better position to come away with a plan that you can explain and execute.

Bill Stronge is a PMP certified Project Manager with a Global CPG organization currently focusing on eBusiness projects. During his 14+ years, he has worked on enterprise-wide applications in both a developer and architect role, as well as a project manager leading teams of various sizes. He can be reached for questions at wstronge@hotmail.com.

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10 comments
dlphcorp
dlphcorp

Great article! As a web supervisor, I'm really having a hard time managing all the projects. Maybe these methods will help solve my problems.

osocram
osocram

Bill, I totally agree with you, I surprising how some people explain how to make an schedule for the project recomend gantt, because many people think that gantt is the rule (even many PMPs), and gantt is only a tool for report the time status of a proyect. if some have interes, the best tool for make a schedule is Critical Path (and PERT), and the best software tool for do that is a spreadsheet. after that, apply the resource leveling. ...and the most recent tool is critical chain...

rbortiz
rbortiz

the author didn't mention the best method for correctly estimate the project time: Critical Chain. Besides the method to estimate activities time, it is also included in this method how to find the resource that is the bottle neck and how to manage the actual status of the project, using the time buffer.

jonw
jonw

I found your paper very useful, thanks. One recommendation since as human beings we are, far too optimistic regarding what we can achieve in a day. May I suggest that the estimation formula be initally adjusted to (2XP + 3XM + O)/6. When the estimators have more experience and the organisation is hitting the estimates then you can adjust it to your proposal. Obviously EVA can be used to validate the estimations once the project is in flight.

PMPsicle
PMPsicle

Actually GANTT is a diagramming method, PERT is an estimation method and Critical Path is a scheduling methodology. GANTT is the arguably the best way to describe the schedule in a visual manner especially as the Task Network diagram becomes more complex with interacting task chains. This is because it intrinsically shows the interactions, and relationships between the various task chains. PERT is one of several methods of estimating a task's effort. It has the advantage of being mathematically simple and defensible, and also provides upper and lower ranges. Having said that, it has a number of issues identified in the last 10 years especially with regards to its use in software development (where the variance can be as high as 500%). Critical Path method is a scheduling and monitoring methodology. Basically, it focuses on the tasks which form the longest chain. By concentrating on those tasks the project manager can reduce their focus to a reasonable level rather than attempting to focus on all tasks in the project. Contrast this with the concept of Critical Chain which concentrates management on the interactions of the various task chains (i.e. Network interactions). All three can be used in the same project -- they are complimentary after all. And in fact GANTT charts are often a prerequisite to CP analysis. To say that one is better than the other is to ignore the basic purpose of each. As for the use of spreadsheets ... yes, if the project is simple enough all that is needed is a spreadsheet. However, for anything larger than a simple project some form of network diagram (AON or AOA) is mandatory in order to visualize the interactions. Glen Ford www.TrainingNOW.ca

DavidR23
DavidR23

As a project manager who works with high uncertainty custom software development projects, I totally agree with Roberto. Check out The book: The Goal and Critical Chain by Eliyahu M. Goldratt

donstrayer
donstrayer

There are several variants of the PERT formula. One I like uses sigma of O and P to adjust the estimate toward P. The greater the variation the less certainty and the more likely the actual will tend toward the pessimistic. But there's little reason to vary from the standard formula. It's the one built in to your tools, such as MS-Project, so using a variant entails extra work with little benefit. It's much more important to give some serious thought to O and P -- what could cause M to be vary, by how much, and how likely it is to occur. PERT is no help if you're just pulling the numbers out of the air.

osocram
osocram

I agree with you, your clarification is more explicit, each technique is definitely value and a good project manager must know how to use them, my previous comment referred to in my experience, there are many leaders of project they want to do everything with Gantt Precisely because they are unaware of these other tools. Very good explanation of the techniques.! Regarding the spreadsheet, I was able to implement control and making decisions better than a chart Gantt, even with projects of more than one year, 250,000 hours, and more than 8600 activities, but it requires experience. Marcos Orozco www.bconsultec.com

PMPsicle
PMPsicle

Actually, the reasoning behind the variants is to acknowledge a basic failure in the PERT methodology. The failure being a bias in the calculation of Pessimistic, Optimistic and Most Likely. The studies which have recommended adjusting the formula have identified the problem as a bias on the part of technical staff to underestimate the three pieces especially with respect to the variance. Typically, the estimated variance is closer to a 2 sigma than the calculation's presumed 6 sigma. Having said that, the suggestion to examine the causes of the variances and the associated risks is a key element in later stages of the calculation of total project cost/time --- specifically risk management. Glen Ford http://www.TrainingNOW.ca

PMPsicle
PMPsicle

I've also driven nails with screwdrivers when a hammer wasn't available. But it's not something I suggest! That's not to say that spreadsheets don't have a use in managing large projects. Just that they aren't the right tool as your primary management tool, especially as the project complexity increases. Glen Ford http://www.TrainingNOW.ca http://www.Can-Da.com

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