Tips and Tricks: Does Your Schedule Pass the Test?

How do you know whether your schedule is good or not? The following are a few tests to see if your CPM schedule is up to par. If you have additional tests that you like, please provide them in the comments. The idea is to collect rules of thumb for identifying good schedules and eliminating bad ones. Here are half a dozen tests to try out on your next schedule:

Test 1: Does the ‘Total Float’ sort or ‘Longest Path’ filter identify a reasonable critical path for the project?

With multiple calendars, the total float/early start sort may not identify the critical path. Some software offers a Longest Path filter to work around this problem. Make sure the longest path is reasonable. Then check the reasonableness of near critical paths. [If you’re using the Longest Path filter, you may have to make a copy of the schedule and start deleting logic ties so that near critical paths show up when the Longest Path filter is rerun]. If the critical path and near critical paths are reasonable, you’re off to a good start.

Test 2: Do any activities have too much float?

Run a total float sort and examine the activities with the most float. Activities with too much float may indicate missing logic ties or logic ties that have been overridden by reporting out-of-sequence progress when updating. Add logic ties, if necessary, to insure that float durations are reasonable and correctly model the current plan.

Test 3: Do any activities have planned durations greater than the update cycle?

Ideally, project activities should be planned at a level of detail so that activity durations are equal to or less than the update cycle [with certain project specific exceptions]. Thus, if a schedule is being updated monthly, planned durations should be 30 calendar days or less. This means that each activity will be in progress for no more than a single update cycle, unless it is behind schedule. By using shorter activities, remaining duration estimates are both easier to make and more accurate, resulting in better status reports for upper management and the project team.

Test 4: Are there any unnecessarily long gaps in workflow when grouping activities by Work Area and sorting by Early Start/Early Finish?

Take a look at an early start/early finish sort grouped by work area, department or phase to get a feel for workflow and resource requirements. Long gaps in an area or phase may indicate less than ideal workflow requiring adjustment of preferential logic ties to create a better plan. In most cases, once work begins in a particular area or on a particular phase of the project, the schedule should allow work to continue uninterrupted in that area or on that phase until it is complete.


Test 5: Are there activities with unnecessary user-assigned constraints?

Since user-assigned constraints override the network logic in calculating early/late dates and float, they should be used sparingly on a project, if at all. A better approach is to use activity durations and network logic to accurately model the project and eliminate constraints. Consider either (1) printing out a constraints listing or (2) running a filter selecting constrained activities. Once you’ve identified all the constraints in the network, you can begin removing them.

Test 6: Are remaining duration estimates accurate?

Too often on a project, remaining duration estimates are automatically generated by reporting activity percents complete at each update. First, make sure that any automatic software link between remaining duration and percent complete is turned off. Next, make sure that every time the schedule is updated, the people responsible for getting the work done provide the remaining durations for activities in progress. Without accurate remaining duration estimates, no downstream dates or contingency times (float) will be accurate, making the schedule a candidate for printing on softer paper.

Try these tests on your project and let us know what you find. And, add your own tips and tricks to the comments below. Good luck and happy scheduling!

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2 Responses to Tips and Tricks: Does Your Schedule Pass the Test?

  1. Bruce Cohoon says:

    An excessive number of logic ties can result in conflicting logic paths with a preliminary effect of “contaminating” the true critical path. The long term effect is that future time impacts will not be correctly measured in terms of float values and completion dates.

    The easiest way to evaluate a completed schedule is to divide the number of relationships by the number of activities. The most ideal resulting number should be 1.2. this means that for every 100 activities in the schedule there are 120 relationships. This results in a VERY tight schedule and I can guarantee that every time delay will be easily identified and the float numbers will reflect it.

    Of important note: This is a very good metric but the goal of 1.2 should ONLY be applied on projects where very tight and reactive schedules are expected, desired and/or required. In project environments where less reactive logic paths are wanted, the calculation is still valid, but the resulting value should be greater than 2.

    Just my 2 cents worth…

  2. David Doughty says:

    Another test (in P6) is to turn on the time of day (I use a 12 hour clock) in the Dates tab under Edit / User Preferences. Very often the time of day is pre-set at midnight which can play havoc with Finish Milestones and finish dates.
    Once it is turned on, scan down your start and finish dates in you Activity Table to see if anything unusual has been calculated. It is also a good way to see if your calendars are in sync.

    Try it!

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