5th Edition PMBOK® Guide—Chapter 6: Techniques for Controlling the Schedule

1. Introduction

There are various tools and techniques listed for monitoring and controlling the schedule, which is what the process 6.7 Control Schedule is all about. Here is the summary of these tools & techniques

The automated tools for controlling the schedule are listed under #2 and #8 below. The last post covered performance reviews, which encompassed the four techniques listed below, the most important of which is earned value measurement.

This post will cover the techniques listed under #3, #4, #5, and #6 below, resource optimization techniques, modeling techniques, leads and lags, and schedule compression. You may note that these techniques are all techniques that are used in setting up the schedule, and are therefore listed under the Tools & Techniques for process 6.6 Develop Schedule.

The purpose of this post will be to see how those same techniques that were used in creating the schedule can also be used to control it as well. It will also explore some of the interrelationships between these techniques, and how some of them can be used in conjunction with each other.

1. Performance reviews Measures, analyzes and compares schedule performance based on data such as actual start and finish dates, percent complete, and remaining duration of work. Techniques used may include:

  • Trend analysis
  • Critical path method
  • Critical chain method
  • Earned value measurement
2. Project Management Software This is a tool (Microsoft Project, Primavera, etc.) which can:

  • Track planned vs. actual dates
  • Report variances from the schedule baseline
  • Forecast the effect of changes on the schedule model
3. Resource optimization techniques Used to adjust schedule due to demand (project time) and supply of resources (resource availability).

  • Resource leveling
  • Resource smoothing
4. Modeling techniques Used to review various scenarios used in risk monitoring to bring schedule model in alignment with project management plan and schedule baseline.

  • What-if scenario analysis: used to assess feasibility of the project schedule under adverse conditions
  • Simulation: calculates multiple project durations based on different sets of assumptions (Monte Carlo analysis)
5. Leads and lags Used to bring project activities that are behind into alignment with the plan.
6. Schedule compression Used to bring project activities that are behind into alignment with the plan.

  • Crashing: adds resources
  • Fast-tracking: activities normally done in sequence are now performed in parallel for part of their duration
8. Scheduling tool Automated scheduling tools contain the schedule model by allowing one to input the scheduling data and to monitor the schedule via the output (the project schedule).

2. Resource Optimization Techniques

It is important to realize that resource optimization techniques as definitely increasing the duration of the project if they are used on activities that are on the critical path (resource leveling), and possibly increasing it if they are used on activities that are not on the critical path (resource smoothing). By rationing or limiting the amount of resources that can be used in any given work period, they may cause the duration of those activities to require additional work periods. If a critical resource, person A, has to work on two different projects every day, then that person will only be available for 4 hours per day rather than 8 hours for each of those two individual projects.

So in a way, it is almost the reverse of schedule compression (see paragraph 6 below), which adds resources that can be used in any given work period in order to reduce the number of work periods required to complete the activity.

One cannot readily think of an scenario where you would want to deliberately add duration to a project, so it is hard for me to think of using resource leveling to control the schedule. However, it may be used in conjunction with certain what-if scenarios (see Modeling Techniques in paragraph 4 below), for example, to figure out how adding an additional project may affect the given project. In that case, it is easy to see that assigning company resources onto project B that are already being used by project A might have the effect, through resource leveling, of causing project A to take longer.

3. Modeling techniques

If there are risks that are uncovered during the monitoring & controlling process that weren’t initially uncovered during the planning process, then the what-if scenarios may be used to see how those risks, if realized, might affect the project schedule.

If the risks are not just one-time occurrences, but systemic risks that occur throughout the project, then Monte Carlo analysis might be able to uncover the probable impact on the project duration by calculating multiple project durations based on the new pessimistic or optimistic (i.e. worst-case and best-case) scenarios created by these systemic risks.

4. Leads and lags

One of the schedule compression techniques (see paragraph 5 below), fast-tracking, takes two activities that were one in sequence and now has them done partly in parallel. In affect, you are taking two activities with 0 lead (or lag) for that matter, and creating a lead for the second activity, based on the number of days before the finish of the predecessor activity that the successor activity is started. So this is one example of how leads can be used to control the schedule.

One would normally not willingly create a lag between two critical path activities, because this would necessarily result in a delay in the project. However, you might want take two activities that are not on the critical path and create a lag called a buffer as part of the critical chain method (one of the techniques listed under #1 in the chart above under Performance Reviews). That buffer could be set equal to the amount of total float that these activities have. Total float, you may recall, is the amount of time activities can be delayed without affecting the critical path, and therefore the length of the project itself. Monitoring the amount of buffer you have versus the amount you planned for, i.e., monitoring the lag between two non-critical path activities, might therefore be a way of monitoring the risk that that non-critical path has of affecting the project schedule as a whole.

5. Schedule compression

If you are in need of compressing the schedule for a project that is taking longer than expected (based on the results of earned value measurements such as schedule variance or SV, or the schedule performance index or SPI), then you may need to resort to crashing activities by adding resources to them, or fast-tracking, by starting a successor activity before the predecessor activity has finished. These compress the schedule by adding cost (in the case of crashing) or risk (in the case of fast-tracking).

Any of the changes suggested by these techniques would then have to be processed as change requests, one of the outputs of the process 6.7 Control Schedule and then these change requests would be reviewed as part of the Perform Integrated Change Control process in Integration Management. This process of change requests will be discussed in the next and final post in this series on Chapter 6, Schedule Management.


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