[Scientific basis of measuring instruments in public health: on the example of LEP progress in the achievements of nursing].

The need for data of professional interventions in public health in general and in nursing in particular has risen sharply over the last years. When it comes to the development and the use of respective measuring instruments, their scientific foundation is normally called into question. The article deals with this problem using as an example the LEP method. The focus lies on questions of methodology and philosophy of science rather than questions concerning the sociology of organization, profession or knowledge. At first the basic problem of measurement in social sciences is outlined using the distinction of first and second order measurements. Then we introduce the construction process of LEP and show, in which way it links the two levels of measurement. In the following paragraphs questions of validity and reliability are addressed as well as the decision to use time as a yardstick. We then show that LEP is not a measuring method to test scientific hypotheses but a valid instrument constructed with the help of social sciences that instructs management decisions. As an information system it combines elements of science, practice and bureaucracy and integrates them at the same time. As a boundary object it provides the basis for a constructive dialogue between the various stakeholder groups.