
Measuring Internal Product Attributes ◾ 355
FPs can form the basis for an eort estimate.
EXAMPLE 8.14
Suppose our historical database of project measurements reveals that it takes
a developer an average of two person-days of effort to implement an FP.
Then we may estimate the effort needed to complete the spelling checker as
118 days (i.e., 59 FPs multiplied by 2 days each).
But FPs are also used in other ways as a size measure. For example,
they can be used to express defect density in terms of defects per FP. ey
are also used in contracts, both to report progress and to dene payment.
For instance, Onvlee claimed that 50–60% of xed priced ...