Page 215 -

186 PART TWO MANAGING SOFTWARE PROJECTS

task has been completed. 11 The remaining 10 percent, although important, can
(1) be delayed until the next increment or (2) be completed later if required. Rather
than becoming “stuck” on a task, the project proceeds toward the delivery date.

7.8 EARNED VALUE ANALYSIS
In Section 7.7.2, we discussed a number of qualitative approaches to project track-
ing. Each provides the project manager with an indication of progress, but an assess-
ment of the information provided is somewhat subjective. It is reasonable to ask
whether there is a quantitative technique for assessing progress as the software team
Earned value provides
a quantitative progresses through the work tasks allocated to the project schedule. In fact, a tech-
indication of progress. nique for performing quantitative analysis of progress does exist. It is called earned
value analysis (EVA).
Humphrey [HUM95] discusses earned value in the following manner:
The earned value system provides a common value scale for every [software project] task,
regardless of the type of work being performed. The total hours to do the whole project are
estimated, and every task is given an earned value based on its estimated percentage of
the total.
Stated even more simply, earned value is a measure of progress. It enables us to
assess the “percent of completeness” of a project using quantitative analysis rather
than rely on a gut feeling. In fact, Fleming and Koppleman [FLE98] argue that earned
value analysis “provides accurate and reliable readings of performance from as early
as 15 percent into the project.”
To determine the earned value, the following steps are performed:
? How do I 1. The budgeted cost of work scheduled (BCWS) is determined for each work task
represented in the schedule. During the estimation activity (Chapter 5), the
compute
earned value to work (in person-hours or person-days) of each software engineering task is
assess progress?
planned. Hence, BCWS is the effort planned for work task i. To determine
i
progress at a given point along the project schedule, the value of BCWS is the
sum of the BCWS values for all work tasks that should have been completed
i
by that point in time on the project schedule.
2. The BCWS values for all work tasks are summed to derive the budget at com-
pletion, BAC. Hence,
BAC = (BCWS ) for all tasks k
k
3. Next, the value for budgeted cost of work performed (BCWP) is computed. The
value for BCWP is the sum of the BCWS values for all work tasks that have
actually been completed by a point in time on the project schedule.

11 A cynic might recall the saying: “The first 90 percent of a system takes 90 percent of the time. The
last 10 percent of the system takes 90 percent of the time.”