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Analysis of negative schedule variance involves looking at your critical path activities to identify those which have been delayed and to look forward at the remaining tasks to see how the schedule might be optimized to make up for the negative variance.
Earned value analysis is just one of the many tools which a PM could use for getting early warning of a negative variance. On projects following an adaptive lifecycle and using sprints, measures such as velocity could be used to provided updated forecasts each sprint.
Agree with Kiron.
CPM (for waterfall )
Leads and lags
Iteration burn-down chart (for Agile) & Agile release planning
you can look at the PMBoK Guide 6.6.2 for the tools and techniques for schedule control.
Mansour mentioned the most of those listed there, and there are more like MTA (milestone trend analysis) that are not explicitly mentioned.
1; you need a comprehensive CPM schedule. By comprehensive I mean activities, durations, dependencies, resource requirements, float, etc
2; you have to think of 'task' delays rather than 'project' delays
3; clearly identify the reason for the delay and how it can be mitigated within the task itself.
4; insert the impact of the delay into the appropriate task(s) and recalculate the schedule.
5: see if the delay can be mitigated within the project and re-establish the initial project float
6; identify a loss of float and acknowledge potential impact on delivery.
Thanks all for your responses
below is one of the response what i got
please note below the different methods that are commonly used to analyze delays:
As-Planned vs. As-Built method
Impacted As-Planned method
Collapsed As-Built or "But for" method
Window Analysis method
As-Planned vs. As-Built Method
The analyst compares the dates and durations of selected activities shown on the as-planned schedule with the actual dates and durations on an as-built schedule and considers the difference to be the delay on the job.This is a very simplistic view of the delay claim because it ignores the following important factors:
The cause of the delays
The timing of the individual delays, their impact on the schedule, and the ability to attribute the correct number of delay days to the correct, responsibleparty
The impact of concurrent delays
The fact that the logic and sequence of the as-planned schedule may have changed through the project due to numerous delaying factors
Impacted As-Planned Method
In this method the analyst lists the excusable delays (or delays where time extension is owed to the contractor) and inserts the extended duration to the relevant activities. The analyst reads the revised completion date, calculates the days between this date and the as-planned completion date, and determines that these are the number of days owed to the contractor. The sources of error in this method follow:
It ignores the actual as-built schedule and events on site.
It assumes that the logic of the as-planned schedule reflectsthe reality on site.
It ignores the inexcusable delays that may have been concurrent to some of these inserted delays, which impacts the number of days owed to the contractor.
Since the analyst is only using the as-planned schedule, this method doesn't incorporate changes in logic and out-of-sequence work.
Collapsed As-Built or "But For" Method
In this method, the analyst takes the actual as-built schedule and takes out the duration of all the excusable delays (delays rightfully owed to the contractor). This revision forms the collapsed as-built schedule. The analyst reads the completion date on the collapsed as-built schedule and considers this date to be the completion date of the project had the contractor not been delayed. The analyst calculates the days between the collapsed as-built and the completion date from the as-built schedule and considers these days to be the days owed to the contractor. The sources of error in this method follow:
It depends on the as-built schedule to be accurate.
The excusable delays removed from the as-built schedule are assumed to be excusable without a complete analysis of these delays, the causes and concurrencies. That means subjective assumptions and judgments have been taken and need to be examined.
It doesn't factor in how the sequence of operation changed, any acceleration that took place,and any recovery that took place because the as-built schedule is a representation of what really happened on site without addressing causes and effects of delays along the way.
In some cases, where an as-built schedule does not exist, the analyst recreates the as-built schedule based on his/her research. This product does not reflect the planned logic of activities or the planned critical path.
Window Analysis Method
This method is based on analyzing the delay over the entire schedule, dividing it into windows with a selected duration, most commonly monthly. The analyst looks at the activities within the selected window and updates the activities, incorporating the delays within the selected window. Updating the selected window changes the as-planned schedule to an as-built schedule up to the end date of the selected window and becomes the basis for projecting the remaining activities from the end of the window to the completion of the project. The sources of error in this method follow:
Need to have accurate as-built information on the start and finish dates of the windows
Need for the original base schedule to be accurate
Delaying activities outside the selected window that have an impact
This method is used in the absence of reliable schedules on the job. In this case, the analyst recreates a schedule based on actual information. The analyst determines the logical ties between the activities to form a retrospective schedule, which becomes the basis for analyzing the effect of the delays. Durations are given to the activities based on reasonable time to finish the various activities. The delays are then inserted in the newly created schedule and then compared with the actual as-built durations to calculate the number of delay days. The sources of error in the method are these:
The analyst has to be very experienced in construction means and methods.
There are a lot of judgment calls by the analyst that need to be examined.
This is usually the preferred method of analyzing delays. In this method, the analyst takes a look at the schedule and actual site progress on the starting date of each delay, and then inserts the delays in the schedule. The new completion date is compared to the original completion date to determine the delay days. This way, the impact of concurrent delays is incorporated, and the new critical path reflects reality on site and effects of the delaying causes. The sources of error in this method occur when the analyst does not have the following:
Good documentation to reflect the actual site progress
Accurate schedule updates
In conclusion, the analyst has to select the best method to use for analyzing delay claims. Each approach has its advantages and drawbacks. Sometimes the nature of the case, available time, document availability, or budget consideration influences the method selection.
1.10 TIME IMPACT ANALYSIS REQUIREMENT
A. When delays are experienced and time extension is requested, submit a written time impact evaluation illustrating influence of changes or delays on current Project contractual completion date.
B. Constructed based on appropriate contemporaneous methods of schedule delay analysis, using fragnet analysis (or window analysis), or time impact analysis approach, or combination or variations of both methods as applicable to extent of the delay.
C. If utilizing fragnet analysis, employ following step-by-step procedure:
1. Update approved schedule, using existing durations, at occurrence of unexpected event without considering impact on schedule.
2. Review updated schedule to determine effect on activities.
3. Modify updated schedule by inserting an activity or activities to reflect projected impact of unexpected event.
4. Recalculate schedule with unexpected event.
5. Compare original updated schedule with modified update to determine effect on updated schedule.
6. Review to determine alternatives and adjust modified updated schedule to mitigate impact of unexpected event.
7. Recalculate modified updated schedule.
D. Owner will evaluate time impact analysis and modified updated schedule. Requests for time extension will be evaluated based upon an analysis of this modified updated schedule. Establish Critical Path and identify Owner-caused delays beyond any interim Milestone, contractual Substantial Completion, and/or contractual Final Completion dates on the Critical Path.
E. Demonstrate estimated time impact based on events of delay, status of construction at that point in time, and event time computation of activities affected by the change or delay. Use existing durations from approved schedule.
F. Time Impact Analysis will be based on the latest approved schedule before a change event happened. If no approved schedule is available, the Contractor shall use the approved baseline schedule for comparison.
G. The Contractor shall use the AACE 52r-06 or AGC’s Recommended Practice when doing Time Impact Analysis.
E.H. Time Impact Analysis shall incorporate all delays (including the AUTHORITY, the CONTRACTOR, and third-party delays without exception) in the time frame that they actually occurred with actual logic ties.
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