Stability analysis of clustering of Norris’ visual analogue scale

Abstract Visual analogue scales are widely used to measure subjective responses. Norris’ 16 visual analogue scales (N_VAS) measure subjective feelings of alertness and mood. Up to now, different scientists have clustered items of N_VAS into different ways and Bond and Lader’s way has been the most frequently used in clinical research. However, there are concerns about the stability of this clustering over different subject samples and different drug classes. The aim of this study was to test whether Bond and