3
Process Performance Model (PPM)??”e
ffort for new de elopment
262 n Interpreting the CMMI
is derived from project information gathered and from the organization??™s metrics
database. The mean value for each PPB element by phase comes from the Mean
column in Table 19.2. The Historical Effort Distribution on line 12 of Table 19.3
comes from project actuals stored in the organization??™s metrics database.
The purpose of the example PPM for effort shown in Table 19.3 is to predict the
total effort for the new development project. This model is designed to predict the
total project effort throughout the life cycle, using more and better estimates and data
as they become available. The example is divided into the following five sections.
PPB Elements (Lines 1??“10)
For each of the elements, the model contains an estimated number of elements
and the mean effort in hours for each applicable phase from the example PPB
shown in Table 19.2. For example, line 2 shows that 75 complex requirements are
estimated, that the mean number of effort hours in the Requirements phase for a
complex requirement is 35, and that the mean number of effort hours in the Design
phase for a complex requirement is 49.
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