In the THE World University Rankings column (22 April), you say that your new global reputational survey includes data on institutions' research and teaching strengths, with teaching-focused staff asked discipline-specific action-based questions to determine where the best undergraduate and postgraduate teaching takes place.
What is your definition of "best" for this purpose, and - given that this is a "global" survey - how can your sample possibly know?
Peter Williams, Malvern.