In mission-driven organizations, we tend to feel a particular irritation when those to whom we answer require us to account for our work with statistics. “Not everything that matters can be quantified!,” we insist – and we’re right. In fact, there’s a powerful argument to be made that the more important an endeavor is, the less likely it is that the endeavor’s success or failure will be easily quantifiable.

I’ll go further, in fact, and say that some of the most important aspects of our work are not only impossible to quantify, but also nearly impossible to assess qualitatively, at least with any degree of reliability. How can you know the real-world impact of a correctly applied metadata tag? How can you know whether the research assistance you provided to a student made any difference to her educational experience or her life? When you declined to purchase one book and decided instead to purchase another one, what exactly did the rightness or wrongness of that decision end up meaning for the people your library serves? Any one of these decisions could turn out to be pivotal in the course of an individual’s life and the institution’s ability to achieve its goals – and any one of them could have little or no real-world impact. Except in very rare cases, we’ll never know which was the case for most of the work we do. 

In light of this reality, it would be all too easy to make one of two common mistakes: