Schedule Analysis

Index

Table of Contents

Schedule Assessment and Analysis

Schedule assessment is the process of determining schedule validity and realism at a given point in time.

Schedule analysis is the process of evaluating the magnitude, impact, and significance of actual and forecast variances to the baseline and/or current schedules. After routine updates, schedule analysis begins with the calculation of the critical path and the determination of any change in the completion date of the project. Analysis results should be reviewed with the project team.

This process may be iterated as needed.

Health Check

Schedule health is determined by monitoring key indicators reflect both good and poor schedule structure and maintenance. Examples of key indicators include the following;

For programme audits this may be recorded in a formal report.

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The following reflects the recommended stoplight criteria used in the above Schedule Health Check:

Schedule Health Check Rating Criteria for missing predecessors, successors less than 5% is green;

The average results are color coded as follows: Red is less than 1.75, Yellow 1.75 to 2.5 and Green greater than 2.5.

Weighting for Overall Schedule Rating

Critical Path Analysis

The schedule may become very dynamic during the implementation phase, and because of this, it is imperative to always know what sequence of tasks is the real driver affecting project completion. It is also important to monitor the consumption of schedule reserve that may exist as part of the critical path. Critical path is essential in making accurate resource and manpower decisions to successfully achieve project completion.

Critical path identification and analysis involves constant review of the validity of included tasks, durations, and types of relationships that are involved in the primary critical path, as well as, near secondary paths. Often changes made to durations and/or logic relationships can be made to shorten the critical path and prevent project completion from moving to the right.

It is extremely important to note the difference between critical path activities and “critical activities”. These two may be, but are not necessarily, the same. In scheduling terms, the critical path is the sequence of activities that are tied together with network logic that have the longest overall duration from time now until project completion. Critical activities may be defined as any tasks which have been deemed important enough to have this distinction assigned to them.

Common characteristics of a credible critical path include the following; it typically begins at time now and proceeds to project completion, the tasks and milestones are tied together with network logic in a sequence that makes sense, the path contains no summary activities, and there are no gaps in time between tasks that cannot be explained. It is recommended that after each update cycle of the PMS the critical path should be identified and compared to the previous month’s critical path. In making this comparison it is important to clearly understand what has changed, why it has changed, and again validate that the sequence of tasks passes the common sense test.

Frequently, during initial PMS development or in later implementation phases, management may determine the overall critical path duration must be shortened. When faced with this situation there are two approaches that are typically used. A technique called “Crashing” the schedule may be employed which involves increasing resources on those critical path tasks where the most cost effective time acceleration is achieved. This approach will definitely result in higher costs so that a time/cost tradeoff should be evaluated when using this method. Another approach called “Fast tracking” the schedule typically involves the identification of tasks on the critical path that can be partially overlapped or possibly even a total parallel implementation. This technique may not always result in higher costs, but definitely could increase risk to the project especially in the area of delays due to rework. Both methods should be considered carefully before using them to shorten the schedule.

Critical path identification and analysis are essential to ensure that management is focusing the necessary resources on the correct tasks to prevent slippage of the project end date. Close monitoring and analysis of the top 3 to 5 paths is also recommended and will ultimately provide the necessary insight to better keep the project under control and on track for successful completion.

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Schedule Performance Trend Analysis

Analysis on past performance can provide much insight into future expectations. Studies conducted using data from past projects clearly reflect performance trends rarely improve after projects reach the 15% completion mark. Project teams should establish sound performance analysis practices from the very start of project implementation.

It is recommended that periodic performance and work-off trend analysis be performed on PMS data. This analysis compares performance rates for accomplishing tasks in the past to the quantity of planned tasks required in future months. Caution should be taken if this analysis reflects an unrealistic bow-wave of tasks scheduled to occur with higher required completion rates than the project has been able to accomplish previously. This situation is indicative of a schedule that is most likely unrealistic. In this type of analysis, if the completion rates projected for tasks scheduled for the next six months are much higher than actual completions accomplished during the past six months, then a closer look should be taken at the type of tasks that are scheduled to evaluate the need for re-planning in order to keep the schedule realistic.

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Another best practice for schedule performance trend analysis uses similar rationale as reflected above, but reflects the results as a schedule efficiency factor. The graphic shown below illustrates how past schedule performance data can be translated into a schedule efficiency rating that can be used to provide insight into schedule heath.

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Many other schedule performance trend analysis techniques are available.

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Baseline vs. Current Comparison and Analysis

During the implementation phase of a project, it is likely that the current schedule will at some point deviate from the baseline schedule. This situation is not unusual and occurs for many reasons. It is very important to routinely conduct comparisons between the baseline and current schedule to identify and monitor significant variances, understand why the variances occurred (i.e. the root cause), and what the impacts are to project completion so that appropriate corrective action can be planned. Tasks that have significant deviations from the baseline may also cause a new critical path or a near secondary path. Resources may need adjusting to accommodate these variances and/or work around plans developed to correct the situation. Please keep in mind that the schedule baseline must correspond to the resource baseline and the earned value baseline, so that if drastic deviations occur between current and baseline schedules, it may signal the need for re-planning and/or additional resources.

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Schedule thresholds should be established by the project management team that aid in identifying and focusing on those variances that should be monitored and managed. Two key factors to be considered in establishing schedule variance thresholds are the number of days a task/milestone has changed from the baseline schedule and also how many days of total slack are associated with those variances. Thresholds may also vary due to the type, length, and complexity of the project being implemented. Thresholds that are agreed upon and established by the project management team should also be applied with the added requirement to provide appropriate variance rationale from the responsible manager or implementation team.

Schedule Reserve Assessment

Adequate schedule reserve appropriately placed in a project schedule is critical to project success. A good rule of thumb to use for schedule reserve is 15-20% of the project’s remaining duration. A schedule risk assessment is a good basis for determining adequate schedule reserve. Schedule reserve should be easily identifiable and strategically placed within the PMS. Generally, it is recommended to create specially labeled tasks for schedule reserve and place the bulk of reserve at the end of the schedule just prior to project completion so that it will be reflected and easily accounted for and managed as part of the critical path sequence. Other smaller blocks of schedule reserve could also be associated with significant key events in the PMS and placed logically just prior to those events. Please note that when smaller blocks of reserve are created and associated with key events within the PMS they may not fall on the project critical and therefore will have no effect on the project completion date.

Throughout the project life cycle, it is important to monitor schedule reserve. It is good practice to maintain a log indicating the changes in schedule reserve and the reason for those changes. Monitoring this metric and comparing it to critical path float not only gives an indication of schedule progress at a high level, but also provides an indication of how optimistic and/or realistic the schedule completion date is.

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Schedule Risk Assessment

A Schedule risk assessment is an important analysis process that uses a specialized tool (typically a Monte Carlo simulation} to evaluate the likelihood of the PMS being achievable. Tasks are given minimum, maximum, and the most likely durations as well as distribution profile. This distribution profile, also known as the probability distribution function (PDF), models the likelihood of task durations between the minimum and maximum values. The information generated aids the determination of an adequate amount of schedule reserve to be included in the PMS before baselining.

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Earned Value Schedule Analysis

Project performance data gained from an earned value management (EVM) system may provide additional management insight into schedule performance.

This process effectively integrates cost and schedule for each PBS element so that a schedule performance index (SPI) and a cost performance index (CPI) can be calculated to provide another means of gaining general insight into schedule and cost variances within the project.


25 January 2009 (7)