Managing Projects with Earned Value Management

Revision as of 13:16, 26 September 2016

Figure 1: The Project Management Triangle

The management of technical projects has become a real challenge in an always more competitive market where effective project Planning and Control approaches need to comply with clients’ requirements^[1]. A project is said to be successfully completed if it satisfies the schedule and budgetary constraints while also fulfilling the technical objectives. This task involves comparing the actual situation with the planned one in terms of Scope, Time and Costs, which together form the Project Management Triangle. To guarantee that all project deliverables are achieved, it is very important that all three dimensions of the project management triangle are monitored and controlled.

However, if any of these dimension are analyzed without taking into account the other two, problems may arise, because only a partial overview of the project status would be provided. For instance, a project may be on budget whilst having accomplished less work than what was planned to be accomplished. On the other hand, a project may also be on budget while having accomplished more work than what was planned. How can time measurements be related to costs? And how can managers have an objective overview of the current state of their projects? To answer these questions an effective project control system should be created, in order to provide timely and accurate information on deviations of costs and time measurements from the objectives established during the planning phase of the project.

This is where Earned Value Management (EVM) comes into play by allowing for both schedule and cost analysis against the physical amount of work accomplished. Today, EVM is considered one of the most powerful techniques used in the management of projects in commercial, government or private environments. The purpose of this article is to provide the reader with a brief but effective guidance to the concept of EVM and to its application.

Background and purpose

Earned Value Management, formerly known as Earned Value, emerged in its embryonic version in the 1960’s as a financial analysis discipline in US Government programs. It was the creation of an Industrial Engineer, named A. Ernest Fitzgerald, whose field of expertise was work measurement.

At that time the latest Project Management tool was the Project Evaluation and Review technique (PERT), whose effective implementation was very difficult due to the limited computing technology available at the time ^[2]. As a consequence, it was not always reliable and timely and therefore not widely used^[2] . The computing problems became even bigger^[3] when a joint Navy/Stanford team decided to include resources in the PERT by adding Cost information, and introducing the PERT/Cost. A weakness of the PERT/Cost, in the eyes of Ernest Fitzgerald, was that it adopted updated estimates as the performance measurement baseline. In order to address this and other issues Fitzgerald founded a consulting firm called Performance Management Corporations (PMC), which delivered, as one of its first products, the highly influential Earned Value Summary Guide, where a first definition of Earned Value was provided:

“Earned Value is a concept – the concept that an estimated value can be placed on all work to be performed, and once that work is accomplished that same estimated value can be considered to be “earned.” The utility of this concept as a management tool is that the summation of all earned values for work accomplished when compared to what was actually expended to perform the effort can provide management with a comprehensible, objective indicator of how the total effort or any identifiable segment is progressing.” (as cited in Morin, James B. (2016)^[2]).

Shortly afterwards, Earned Value started being introduced and validated in the Ballistic System Division with its implementation in the Air Force’s Minuteman Program. Earned Value won the battle against the PERT/Cost methodology, which was concurrently proposed to the Air Force as a valid alternative. The determining criteria for sticking with Earned Value relied on the inflexibility of its basis for measurements, which in the case of PERT/Cost could be adjusted to hide overruns. The PERT/Cost methodology encountered the Air Force rejection ^[4] and by mid-1960's it was decided that the Minuteman Earned Value approach would be the Air Force standard. Soon Earned Value was expanded to a Department of Defense-wide requirement.

Theory of Earned Value Management

The process of controlling is fundamental to the success or failure of any project. Therefore, it is likewise important to measure the project performance throughout the whole life of the project. Earned Value Management is a project management technique used for measuring, at any time, the progress and the integrated performance of a project in an objective way. It is an approach that effectively combines the scope of a project with time and costs parameters and allows alerting to deviations from budget and schedule baseline. With this methodology it is possible not only to see how a project is performing, but to predict future performance as well. In fact, it is also able to estimate the project completion date and final cost and to provide accurate forecasts of performance problems, which can be a fundamental contribution when managing a project.

The concept

EVM's core concept is "Earned value", which means the value assigned to work which has been accomplished at a certain time. By comparing this monetary value to the planned budget and to the actual cost to that work, EVM is able to measure and evaluate the status of a project at any given point in time. The specific metrics used in EVM can act as early warning signals to timely spot problems or to exploit new project opportunities.

A simple example

DTU is going through an architectural renovation project which involves, among other activities, replacing every outdoor dining table of the campus with new ones. A team has been assigned to this task and the plan is the following:

Figure 2: Visual representation of the example

Figure 3: Cost and Schedule Variances

• 15 batches of 10 tables (150 tables in total) need to be installed
• It is planned to install 3 batches per day (30 tables)
• The budgeted cost per table is 200 dkk. (total budget = 30,000 dkk)

After the first day:

• 25 tables have been installed against the 30 which were planned. (The drill broke down and caused delays).
• The Total Cost for the day was 6,800 dkk. This is because a new drill has been rented and costs 1,800 dkk per day.

Basic EVM calculations for the first day:

• Budgeted Cost (BC): 30 tables planned * 200 dkk/table planned = 6,000 dkk
• Earned Value (EV): 25 tables installed * 200 dkk/table installed = 5,000 dkk
• Actual cost (AC): 25 tables installed * 200 dkk/table installed + 1,800 dkk for the new drill = 6,800 dkk

A visual representation of these three parameters is shown in Figure 2, which clearly shows that there is a difference between what it was planned and what has been accomplished. This difference regards both Cost and Schedule:

• On a Cost level the difference between Earned Value and Actual Cost is called Cost Variance and in the example is equal to: 5000 - 6800 = -1800

It is a negative value, which means that the project is, at Day 1, over budget.

• On a Schedule level the difference between Earned Value and Budgeted Cost is called Schedule Variance and for this case is equeal to: 5000 - 6000 = -1000

Again, the value is negative, which means that the project is, at Day 1, behind schedule.

A visual representation of the variances is provided in Figure 3

If no action is taken to modify the current performance of the project, its final state can easily be plotted by extending the Actual Cost into the future. This let us calculate the Estimate at Completion (EAC), which is the Actual Cost of the project at the time of its completion. By comparing EAC to the Budget at Completion (BAC), the Project Slip and the Cost Overrun of the entire project can also be calculated.

The example above represents a very simple situation for evaluating the progress of a single task. In reality it is usually significantly more difficult to determine the realistic progress of a project. However, this is an essential prerequisite to ensure the accuracy and meaningfulness of the Earned Value Management methodology.

EVM Terminology

In the previous section a few technical terms of EVM have been briefly introduced. These are extremely important since Earned Value Management uses a specific terminology which needs to be known and fully understood by all the people involved in the application of this methodology. This section presents and discusses the EVM key terms by dividing them three categories:

1. The three basic metrics - to calculate the difference between plan, cost and progress.
2. The project performance metrics - to evaluate the current project performance, in terms of costs and time.
3. The project forecasting metrics - to estimate the project duration and total cost, given the current performance.

The three basic metrics

The three key parameters of EVM are the Planned Value (PV), the Earned Value (EV) and Actual Costs (AC). By calculating EV and AC during a project and by comparing it with PV a manager can draw conclusions on the performance of a project. The definitions of these fundamental metrics are given in Table 1.

Figure 4: EVM metrics. Source: http://www.chambers.com.au/glossary/earned_value_management.php.

Project Performance

The Earned Value methodology is based on monitoring the three basic metrics over the life of the project. Through some basic calculations they provide important information on how the project is doing. This information is expressed in the form of other metrics (or indicators) which are divided into two sub-categories:

• Variances, presented in Table 2
• Indices, presented in Table 3.

Table 2: EVM Indicators: Variances.

Earned Value Variances
Cost Variance (CV)	The difference between Earned Value and Actual Cost. The Cost Variance shows whether and to what extent the project is under or over budget.	means under budget means over budget
Schedule Variance (SV)	The difference between Earned Value and Planned Value. The Schedule Variance shows whether and to what extent the project is ahead of or behind the approved schedule.	means ahead of schedule means behind schedule

Table 3: EVM Indicators: Indices

Earned Value Indices
Cost Performance Index (CPI)	The ratio between Earned Value and Actual Cost. It is an indicator of the project cost efficiency.	means better progress for the money means less progress for the money
Schedule Performance Index (SPI)	The ratio between Earned Value and Planned Value.	means more work performed than scheduled means less work performed than scheduled
Project Percent Complete (PPC)	Percent of project work complete. It is the ratio between Earned Value and Budget at Completion, expressed as a percentage.
To Complete Performance Index (TCPI)	It represents the efficiency required to complete the project on budget. It is the ratio between the planned cost of work that still needs to be complete and the amount of money remaining.

Four Performance Scenarios

Figure 5: Four different Time-Cost Scenarios. Source: http://www.pmknowledgecenter.com/dynamic_scheduling/control/earned-value-management-overview-project-performance-scenarios


Given the cost and time dimensions and their possible variances (zero, positive or negative), nine different project performance situations can occur.

• Scenario 1: on time, over budget
• Scenario 2: on time, on budget
• Scenario 3: on time, under budget
• Scenario 4: early, over budget
• Scenario 5: early, on budget
• Scenario 6: early, under budget
• Scenario 7: late, over budget
• Scenario 8: late, on budget
• Scenario 9: late, under budget

Excluding the “on time” and/or “on budget” situations, four scenarios (4, 6, 7 and 9) are left. They are visually represented in Figure 5, that refers to an example of a project with a planned duration of 9 weeks and the actual time equal to week 6.

Figure 5 shows the three EVM key parameters and the SV and CV under the four remaining scenarios. Depending on the SV values, the project is late or early, while the CV determine whether the project is under or over budget.

Project Forecasting

One of the most significant aspects of the EV approach relates to the Estimates at Completion (EAC) for a project. These can also be generated for a contractor and they reflect the actual performance to date and a rational prediction of the future costs of the project. Different techniques have been developed to compute the EAC and hereby the most frequently used are presented. EACs can also be compared to the initial BAC, to estimate the Variance at Completion.

Table 4: EVM Indicators: Forecasts

Earned Value Forecasts
Estimate at completion (EAC)	The estimated total cost at project completion. As the project advances there might be unexpected events, delays and circumstances that may cause variations between the actual final cost and the planned final cost (BAC). EAC is a way to estimate/project the planned cost at the end of the project, based on the data available at a certain time. Depending on the information available and the contingency of the situation, three different formulas can be used to calculate the EAC: (1) used when it is believed that the project will keep spending at the same rate from now onwards, for example because of reasons that are likely to continue. (2) used when it is believed that the project's future expenditure will go on at the original planned amount, for example because of unexpected events that are not likely to happen again. (3) used when it is believed that both cost and schedule performance at a certain time will affect the future cost performance.
Variance at completion (VAC)	The variance at the completion of the project, i.e. the difference between the new estimate at completion and the planned total cost at the project´s completion. By comparing the projected EAC with the original Budget at Completion it is possible to determine whether a project is within budget at any point in time. This is basically done through the Variance at Completion. This metric carries a very important information [1] since it is strictly related to the project’s profitability. If we forecasted that the project will be over budget, then the VAC will take up a negative value. If we forecasted that the project will be under budget, then the VAC will take up a positive value.

Application of Earned Value Management

How to implement Earned Value Management

In order for a company to effectively apply EVM there are a series of steps that need to be carried out. These were gathered by Fleming (1998) ^[4] in ten "must-do's" that build up an application framework valid for projects of any size, in any industry:

1. Define the Scope of Work. The foundation of EVM lies is defining the work scope of the project by deconstructing its Statement of Work (SOW) into discrete components, which will build up the Work Breakdown Structure (WBS).
2. Define a bottom-up plan. All the critical processes, such as the work scope definition, scheduling and estimating resources have to be integrated into into an integrated plan of detailed cells named Control Account Plans (CAPs). The real performance measurements will take place within each CAPs and the total project’s performance will be the summation of the single CAPs' performance. Every CAP can be considered as a subproject of the main project.
3. Formally schedule CAPs. Each of the defined CAPs needs to be planned and scheduled with a formal scheduling system. In earned value terms, this scheduled work represents the planned value of the project. The outcome of this step is the project master schedule, which constitutes the project manager’s defined planned value for everyone to follow.
4. Assign each CAP to an executive for performance. Assigning every CAP to a functional executive for performance effectively commits that person to oversee the performance of each CAP. It is argued by Fleming (1998)^[4] that companies should assign a senior functional person to each CAP, rather than a functional employee. By doing so, a strong commitment from the functional executives will be ensured.
5. Define a baseline that summaries CAPs. The total project performance measurement baseline must be defined, based on the summation of the CAPs' baselines.
6. Measure performance against schedule. The schedule performance of the project must be periodically measured against its planned master project schedule, in order to compute the difference between the work that has been scheduled and the work accomplished (schedule variance). At this point the behind-schedule tasks are assessed, regarding their criticality to the project. If a late task is on the critical path, or if a task involves a high risk, actions can be taken to get the late task back on schedule.
7. Measure the cost efficiency against the costs incurred. The project’s performance efficiency rate needs to be periodically measured, in terms of difference between the value of work performed and the costs incurred to accomplish the work provides the cost-efficiency factor (cost variance).
8. Forecast the final costs based on performance. The final cost of the project needs to be periodically forecasted based on its performance against the plan. Here is when EAC's are calculated
9. Manage the remaining work. The results achieved at a certain time in a project, no matter if good or bad, are “sunk costs”, gone forever. Therefore, any improvements in performance must derive from future work. It is thus fundamental to quantify the value of the work that still needs to be completed to stay within the objectives set.
10. Manage changes in baseline. Any performance baseline becomes invalid if it does not incorporate changes that may have occurred over the project's duration. Therefore, the baseline must be adapted to changes and updated.

Areas of application

EVM has proved to be a valuable methodology in many different domain and for projects of any degree of complexity. Therefore, it should be considered as a valid project management approach every time managers could benefit from receiving early warning cost signals, able to modify the ultimate direction of the project.

Some of the industry where EVM has been successfully implemented are:

• Information Technology ^[5]
• Construction ^{[6] [7]}
• Professional Services ^[5]
• Government and public work ^[5]
• Energy and power ^[5]
• Software development ^[8]
• Manufacturing ^[5]

Within these areas, EVM is currently applied by both private users and governments and with different levels of maturity. From a geographical point of view EVM is widely used in most parts of the world, with an higher popularity in US, Canada, Australia, New Zeland and Sweden compared to the Middle East and the rest of Europe. ^[5]

Limitations

It has been shown the potential of Earned Value Management as a powerful management system, able to integrate cost, schedule, and technical performance. However, this approach has some limitations:

1. EVM's use depends on a wide and not-so-intuitive vocabulary, which might be an obstacle when it comes to communicate both within the team involved in EVM and with people outside the team, including other managers in the company and/or possible stakeholders. This leads to a poor understanding of EVM (Kim et al., 2003)^[9], which represents an obstacle to its implementations. This is particularly true for organisation which are new to EVM. On the other hand, when a team excels in the use of EVM it might be hard to agree on which formulas to use in order to objectively evaluate the project performance.
2. It requires data which might be difficult to collect e.g. real-time and accurate information from the people directly involved with the works. This could directly affect the quality of the EVM parameters.
   • For instance, a CPI higher than 1.0 suggests that there is an under-run of costs. However, this condition could simply be due to lagging costs, slow to be registered in the organizational cost ledger. A reason for this could be that some activities of the project may be outsourced and therefore, there might be a time mismatch between the earned value measured "on spot", and the actual payment of the outsourced labor invoices, which, according generally takes more time than the recording of labor^[10].
3. The first step for any EVM implementation requires to to define, schedule and budget the work to be accomplished. Therefore, for highly complex and detailed project the EVM approach requires increased time, effort and expertise compared to smaller projects. As a project's level of detail increases, the frequency of using EVM diminishes, according to Kim (2003). ^[9].
4. It generally requires putting in place some kind of infrastructure (e.g. a software) to support the EVM process and be able to generate the data and timely reports required. Generally it is also required to combine the new tools and techniques with other existing systems. As argued by Shechet and Patton (2007)^[11] this requires a lot of commitment and effort.
5. Although it takes into account Cost, Schedule and Scope of Work, Earned Value Management does not assess the Quality dimension of the Project Management Triangle. Since no quality control is factored into EVM, a project that is on time and on budget could still be of low quality.
6. It is not a stand-alone tool: EVM is not sufficient ‘per se’ to monitor projects and programs. Therefore, it must be combined with other methods. One tool typically used with EVM is the critical-path method (CPM), which can use the EVM's WBS activities as input. Other techniques that can be integrated with EVM include Gantt charts, milestones, work authorisation methods and quality control. Combining these techniques together enhances the benefits of EVM.
7. Finally, EVM does not provide solutions, i.e. the output of EVM analysis does not say to managers which actions to take in order to change the performance of the project. The lack of an explicit connection to possible management action is considered by Lipke (2004)^[12] as one of the main deficiencies of the EVM methodology.

An extension to Earned Value Management

A peculiarity of EVM is that at the conclusion of a project which is behind schedule, the Schedule Variance (SV) is equal to zero and the Schedule Performance Index (SPI) is equal to one.  Therefore, a project that was completed late, according to Earned Value metrics, seems to have a perfect schedule performance. To solve this ambiguity an extension of EVM, called Earned Schedule was introduced in 2003. Earned Schedule (ES) is an innovative analytical technique that finds a solution to the EVM dilemma by using time-based performance indicators against the cost-based indicators used by EVM. It directly derives from EVM and it does not require any additional data in order to be implemented.

Annotated Bibliography

List and short description of the main references used to sustain this wiki article:

• Nghi M, Nguyen, Ph.D., PE, PMP. The Application of Performance Measurement Technique in Project Management: The Earned Value Management (EVM) Approach. Retrieved from: http://www.ndv-projectmanagement.com/pdf/The%20Application_EVM-NN.pdf ^[1]

This technical seminar represents an excellent summary on the theory about Earned Value Management and an effective guidance to its real application. It takes into account the contractors’ and owners’ perspective and it shows the importance of EVM in better managing projects through effective planning, controlling and reporting. It is a reading of high practical relevance, particularly recommended for managers and practitioners interested in knowing how to implement the EVM methodology in their organisations, from the preparation until the actual implementation.

• Morin, James B. (2016). How it all began: the creation of Earned Value and the evolution of C/SPCS and C/SCSC. The Measurable News. Page 15-17. ^[2]

An article that documents the origins of today’s Earned Value Management methodology and describes how and why the Earned Value concept was created in the US back in the 60’s. It provides the reader with a good overview of the context in which Earned Value started being used and it describes how it was developed and accepted as a powerful Project/Program Management tool within the US Air Force’s Minuteman Ballistic Missile system and the Department of Defence.

• ^[5]

• Virle, Rajesh and Mhaske, Sumedh (2013) Application of Earned Value and Earned Schedule to Construction Project. International journal of Scientific Engineering and Research (IJSER). Volume 1 Issue 1. ^[6]

A paper dedicated to how to apply Earned Value Management and Earned Schedule (an extension of EVM) in Construction Projects. The authors stresses the importance of EVM in providing project managers, executives and other stakeholders with the opportunity of visualizing the project’s status throughout its entire life. The article is useful not only for people interested in the application of EVM in construction projects but also in any other sector. In fact, it gives a brief and practical overview on the concept and application of EVM and Earned Schedule.

• Khamindi, Mohd. Faris, Ali, Waris and Idris, Arazi (2011). Application of Earned Value Management System on an Infrastructure Project: A Malaysian Case Study. International Conference on Management and Service Science IPEDR vol.8 IACSIT Press, Singapore. ^[7]

An academic paper that provides a brief description of a real-case application of EVM in infrastructures: the construction project of a railway track in Malaysia. The authors go through the different steps of EVM starting from the contractor scope of work and the schedule charts and proceeding with the physical progress reports and the budgeted and actual cost reports. It gives a clear overview of how EVM could be used in practice for the schedule and cost control of construction projects.

• Tamara, Sulaiman and Hubert, Smits (2007). Measuring Integrated Progress on Agile Software Development Projects. Methods & Tools (on-line journal). ^[8]

An article that discusses the application of Earned Value Management in Software Development. It contains a brief introduction to EVM as well as to the concept of Agility in software development. It then presents an adaptation of EVM, called AgileEVM, that is based on the Scrum framework but uses traditional EVM calculations. It is argued by the authors that software development process can benefit from the use of AgileEVM because of its ability in providing an objective analysis easy to share within teams and with management and customers. It is a recommended reading for anybody interested in the application of EVM to this particular area of Software development and in how to combine the Agile Methods with EVM.

• Shu, Chen and Xueqing, Zhang (2012). An Analytic Review of Earned Value Management Studies in the Construction Industry. Construction Research Congress 2012 © ASCE 2012. Page 236-246.^[9]

A paper that undertakes a review covering research in the EVM area. It critically discusses the advantages and disadvantages of EVM.

• EVMS Education Center (2012) Basics concepts of Earned Value Management (EVM). Retrieved from https://www.humphreys-assoc.com/evms/basic-concepts-earned-value-management-evm-ta-a-74-t-1_11.html

The article represents an introduction to the basics of Earned Value Management and covers the main EVM steps from the initial project planning phase until the execution of the plan and data maintenance, going through techniques of data analysis and baseline adjustments. It refers to the Standard for EVM and addresses the benefit that this methodology can bring to both contractors and customers.

• Patton, LTC Nanette and Shechet, Allan (2007). EarnedValue Management: Are ExpectationsToo High?. CrossTalk- The Journal of Defense Software Engineering.^[11]

An article where the authors use their experience with IT and aerospace projects to identify potential difficulties in the application on EVM in this domain together with risk mitigation strategies to counter those difficulties. One of the key message is that when agencies apply EVM, especially for the first time, they should train their managers not only in EVM processes but also in human behaviors and management styles. The authors argue that this is fundamental in order to avoid major problems that can result from the implementation of EVM. It is a particularly relevant reading for those interested in applying EVM in IT projects and for examining the behavioural and human dimension of the EVM application context.

• Lipke, Walt. (2004) Connecting Earned Value to the Schedule. The Measurable News. ^[12]

A paper that looks into the connection between the Earned Value Management approach and the project schedule through the use of the Earned Schedule (ES) concept. The author critically analyses the EVM technique and its main metrics and introduces a new measure to indicate the adherence to the project plan, the P – Factor.

References

1. ↑ ^{1.0 1.1 1.2} Nghi M, Nguyen, Ph.D., PE, PMP. The Application of Performance Measurement Technique in Project Management: The Earned Value Management (EVM) Approach. Retrieved from http://www.ndv-projectmanagement.com/pdf/The%20Application_EVM-NN.pdf
2. ↑ ^{2.0 2.1 2.2 2.3} Morin, James B. (2016). How it all began: the creation of Earned Value and the evolution of C/SPCS and C/SCSC. The Measurable News. Page 15-17.
3. ↑ Fleming, Quentin W. and Koppelman, Joel M. (2005) Earned Value Project Management, Third Edition, Project Management Institute. Page 28.
4. ↑ ^{4.0 4.1 4.2} Fleming, Quentin W. and Koppelman, Joel M. (1998) Earned Value Project Management. A Powerful Tool for Software Projects. Primavera Systems, Inc. CROSSTALK The Journal of Defense Software Engineer. Page 20.
5. ↑ ^{5.0 5.1 5.2 5.3 5.4 5.5 5.6} Song, Lingguang. A Global and Cross-Industry Perspective on EVM Practice & Future Trend. Construction Management Department. University if Houston. Retrieved from http://www.mycpm.org/wp-content/uploads/2012/01/RS-PS-16.pdf
6. ↑ ^{6.0 6.1} Virle, Rajesh and Mhaske, Sumedh (2013) Application of Earned Value and Earned Schedule to Construction Project. International journal of Scientific Engineering and Research (IJSER). Volume 1 Issue 1.
7. ↑ ^{7.0 7.1} Khamindi, Mohd. Faris; Ali, Waris and Idris, Arazi (2011). Application of Earned Value Management System on an Infrastructure Project: A Malaysian Case Study. International Conference on Management and Service Science IPEDR vol.8 IACSIT Press, Singapore.
8. ↑ ^{8.0 8.1} Tamara, Sulaiman and Hubert, Smits (2007). Measuring Integrated Progress on Agile Software Development Projects. Methods & Tools.
9. ↑ ^{9.0 9.1 9.2} Shu, Chen and Xueqing, Zhang (2012). An Analytic Review of Earned Value Management Studies in the Construction Industry. Construction Research Congress 2012 © ASCE 2012. Page 238
10. ↑ Quentin W. Fleming and Joel M. Koppelman, Primavera Systems, Inc. (2016) The two most useful earned value metrics: the CPI and the TCPI. The Measurable News. Page 23-25.
11. ↑ ^{11.0 11.1} Patton, LTC Nanette and Shechet, Allan (2007). EarnedValue Management: Are ExpectationsToo High? CrossTalk- The Journal of Defense Software Engineering. Page 12. .
12. ↑ ^{12.0 12.1} Lipke, Walt. (2004) Connecting Earned Value to the Schedule. The Measurable News. Page 1.