Simpson's Paradox as a challenge in library assessment: an example using LibQUAL+ Long and LibQUAL+ Lite data

摘要

Many librarians may be unaware of Simpson's Paradox1 (Simpson, 1951). Simpson's Paradox involves the phenomenon that relationships or patterns in score means may disappear, or even reverse, when nested data are analysed at different hierarchical levels (eg, for users across all libraries completing a library service quality assessment, versus separate analyses computed at each individual library; or for users across all branches of a library, versus separate analyses computed for each branch with the same library). Librarians need to be aware of this phenomenon, lest they reach wildly incorrect interpretations of their assessment results. The purpose of our paper is to explain and illustrate Simpson's Paradox.