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CHAPTER 4 SOFTWARE PROCESS AND PROJECT METRICS 81

can be used either as a noun or a verb, definitions of the term can become confus-
ing. Within the software engineering context, a measure provides a quantitative indi-
cation of the extent, amount, dimension, capacity, or size of some attribute of a product
or process. Measurement is the act of determining a measure. The IEEE Standard
Glossary of Software Engineering Terms [IEE93] defines metric as “a quantitative mea-
sure of the degree to which a system, component, or process possesses a given
attribute.”
When a single data point has been collected (e.g., the number of errors uncovered
“Not everything that in the review of a single module), a measure has been established. Measurement
can be counted
counts, and not occurs as the result of the collection of one or more data points (e.g., a number of
everything that module reviews are investigated to collect measures of the number of errors for each).
counts can be A software metric relates the individual measures in some way (e.g., the average
counted.” number of errors found per review or the average number of errors found per per-
Albert Einstein son-hour expended on reviews. 1
A software engineer collects measures and develops metrics so that indicators
will be obtained. An indicator is a metric or combination of metrics that provide insight
into the software process, a software project, or the product itself [RAG95]. An indi-
cator provides insight that enables the project manager or software engineers to
adjust the process, the project, or the process to make things better.
For example, four software teams are working on a large software project. Each
team must conduct design reviews but is allowed to select the type of review that it
will use. Upon examination of the metric, errors found per person-hour expended,
the project manager notices that the two teams using more formal review methods
exhibit an errors found per person-hour expended that is 40 percent higher than the
other teams. Assuming all other parameters equal, this provides the project manager
with an indicator that formal review methods may provide a higher return on time
investment than another, less formal review approach. She may decide to suggest
that all teams use the more formal approach. The metric provides the manager with
insight. And insight leads to informed decision making.

4.2 METRICS IN THE PROCESS AND PROJECT DOMAINS
Measurement is commonplace in the engineering world. We measure power con-
sumption, weight, physical dimensions, temperature, voltage, signal-to-noise ratio . . .
the list is almost endless. Unfortunately, measurement is far less common in the soft-
ware engineering world. We have trouble agreeing on what to measure and trouble
evaluating measures that are collected.

1 This assumes that another measure, person-hours expended, is collected for each review.