Since most of the people who are typically involved with forest inventories may not have been trained in how to gather inventory data through personal interviews with forest users, this chapter offers some practical advice to such individuals. The chapter argues that the overall quality of data derived from the NFA interview component depends on how four critical questions are addressed: (1) What does the NFA ask forest users? (2) Who does the NFA ask? (3) How does the NFA ask? and (4) How does the NFA verify data quality?

The concepts of validity and reliability are introduced as central criteria for assessing the quality of the NFA interview results and several practical tests are explained. The suggested approach to quality control promises to both simplify and strengthen the interview results without great costs in time and money. The benefit for paying attention to this advice includes improved credibility of the NFA results and higher likelihood of the NFA affecting future policy decisions. An NFA that is effective in capturing the perceptions of local forest users with regards to their forest use is not only in a better position to understand what factors are causing observed changes in forest conditions, but may also show how these changes are likely to affect different groups of people within a given country.