Justification will be based on empirical data that can be clearly understood by all those involved in the decision making process. What can be measured Measurement is the key factor in any software quality assurance program. But effective use of measurement is dependent on careful data collection, which is notoriously difficult, especially when data must be collected across a diverse set of projects. Thus, data collection is becoming a discipline in itself, where specialists work to ensure that measures are defined unambiguously, that collection is consistent and complete, and that data integrity is not at risk. But it is acknowledged that metrics data collection must be planned and executed in a careful and sensitive manner.
Data collection is also essential for scientific investigation of relationships and trends.
Good experiments, surveys and case studies require carefully-planned data collection, as well as thorough analysis and reporting of the results. Measurements can be performed on all types of software regardless of the technology or methodology used in their creation. The level to which the WBS is decomposed depends on the degree of insight required by management or project sponsorship. Organizations usually get rather ambitious in the beginning of a project and decompose the WBS too far - which then requires too much work to maintain it and the whole system flounders. Worse, if it is decomposed too far, the staff's valuable time is wasted just tracking their own hours.