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130 PART TWO MANAGING SOFTWARE PROJECTS

Each of the complexity weighting factors is estimated and the complexity adjust-
ment factor is computed as described in Chapter 4:

Factor Value
Backup and recovery 4
Data communications 2
Distributed processing 0
Performance critical 4
Existing operating environment 3
On-line data entry 4
Input transaction over multiple screens 5
Master files updated on-line 3
Information domain values complex 5
Internal processing complex 5
Code designed for reuse 4
Conversion/installation in design 3
Multiple installations 5
Application designed for change 5
Complexity adjustment factor 1.17
Finally, the estimated number of FP is derived:

FP estimated = count-total x [0.65 + 0.01 x (F )]
i
FP estimated = 375
The organizational average productivity for systems of this type is 6.5 FP/pm. Based
on a burdened labor rate of $8000 per month, the cost per FP is approximately $1230.
Based on the LOC estimate and the historical productivity data, the total estimated
project cost is $461,000 and the estimated effort is 58 person-months.

5.6.4 Process-Based Estimation
The most common technique for estimating a project is to base the estimate on the
process that will be used. That is, the process is decomposed into a relatively small
set of tasks and the effort required to accomplish each task is estimated.
XRef Like the problem-based techniques, process-based estimation begins with a delin-
A common process eation of software functions obtained from the project scope. A series of software
framework (CPF) is process activities must be performed for each function. Functions and related soft-
discussed in ware process activities may be represented as part of a table similar to the one pre-
Chapter 2.
sented in Figure 3.2.
Once problem functions and process activities are melded, the planner estimates
the effort (e.g., person-months) that will be required to accomplish each software process
activity for each software function. These data constitute the central matrix of the table
in Figure 3.2. Average labor rates (i.e., cost/unit effort) are then applied to the effort
estimated for each process activity. It is very likely the labor rate will vary for each task.
Senior staff heavily involved in early activities are generally more expensive than junior
staff involved in later design tasks, code generation, and early testing.