On the linearity of predefined and self-anchoring Visual Analogue Scales.

Two functional measurement studies were conducted to test the effect of two types of end anchors on the linearity of Visual Analogue Scale (VAS) data. With the first type of end anchors, participants responded to the stimuli using a VAS with predefined end anchors. With the second type, respondents defined the end anchors in terms of their own assumptions, perceptions, goals and values. The results show that VASs can be considered as linear scales and that the type of end anchors used has no effect on the linearity of the VAS data.