Specify Measures

Measurement objectives are refined into precise, quantifiable measures.

Measures may be either “base” or “derived.” Data for base measures are obtained by direct measurement. Data for derived measures come from other data, typically by combining two or more base measures.

Examples of commonly used base measures include:

• Estimates and actual measures of work product size (e.g., number of pages)
• Estimates and actual measures of effort and cost (e.g., number of person hours)
• Quality measures (e.g., number of defects, number of defects by severity)

Examples of commonly used derived measures include:

• Earned Value
• Schedule Performance Index
• Defect density
• Peer review coverage
• Test or verification coverage
• Reliability measures (e.g., mean time to failure)
• Quality measures (e.g., number of defects by severity/total number of defects)

Derived measures typically are expressed as ratios, composite indices, or other aggregate summary measures. They are often more quantitatively reliable and meaningfully interpretable than the base measures used to generate them.

• Identify candidate measures based on documented measurement objectives. The measurement objectives are refined into specific measures. The identified candidate measures are categorized and specified by name and unit of measure.
• Identify existing measures that already address the measurement objectives. Specifications for measures may already exist, perhaps established for other purposes earlier or elsewhere in the organization.
• Specify operational definitions for the measures. Operational definitions are stated in precise and unambiguous terms. They address two important criteria:
  • Communication: What has been measured, how was it measured, what are the units of measure, and what has been included or excluded?
  • Repeatability: Can the measurement be repeated, given the same definition, to get the same results?
• Prioritize, review, and update measures. Proposed specifications of the measures are reviewed for their appropriateness with potential end users and other relevant stakeholders. Priorities are set or changed, and specifications of the measures are updated as necessary.