A third set of influences comes from the specific analytical goals of each health statistics study or survey.
They may aim to:
Track change over time
Identify new treats
Establish a base line to measure changes
Compare the conditions of groups
Identify the etiology of disease
Measure the presence of risk factors for disease
Each purpose sets different analytical requirements that shape what is collected, the analysis and how it is reported.
The impact of the variety of perspectives is to increase confidence in health statistics reports because:
The variety of approaches is a source of robustness and
The multiple sources provide cross validation—they help us to see if a particular set of facts is dependent on [and therefore subject to the limitations of one method] or robust [and therefore reflected in several approaches.]