5.4 What are floor and ceiling effects in outcome measurement?

Table 5.4: Description of Floor and Ceiling Effects

Measurement Property	Description
Floor effect	Floor effect occurs when responses on a measure, questionnaire or scale cluster at the more negative health state end of the scale. For instance, if the scale were administered a second time, there would be no room to detect any possible deterioration in health, even if it had occurred.
Ceiling effect	Ceiling effect occurs when responses on a measure or questionnaire cluster at the more positive health state end of the scale. This means that if the scale were administered a second time, there would be no room to detect any possible improvements in health, even if they had occurred.

Measurement Property

Description

Floor effect

Floor effect occurs when responses on a measure, questionnaire or scale cluster at the more negative health state end of the scale.

For instance, if the scale were administered a second time, there would be no room to detect any possible deterioration in health, even if it had occurred.

Ceiling effect

Ceiling effect occurs when responses on a measure or questionnaire cluster at the more positive health state end of the scale.

This means that if the scale were administered a second time, there would be no room to detect any possible improvements in health, even if they had occurred.