An "open-transformed scale" for correcting ceiling effects and enhancing retest reliability: the example of pain.

The use of closed scales (with anchors at each end) to measure pain was found to produce ceiling effects characterized by a deceleration of ratings toward the upper end of the scale. This was consistent with previous research. Apart from producing nonlinear functions, the closed scale also limited test-retest reliability because of subjects' tendencies to correct their distorted ratings in subsequent trials. However, an open-ended scale coupled with transformation of reported ratings into a decile scale virtually eliminated the ceiling effect, thus producing consistently linear functions and maximizing test-retest reliability. This finding may have implications for the measurement of other sensory and psychological phenomena, especially those in which the property evaluated varies in a continuous fashion.