| has gloss | eng: }} General problem and simple example In statistics and the sciences, a ceiling effect is an effect whereby a measurement cannot take on a value higher than some limit or "ceiling", which is imposed not by the phenomenon being measured, but rather by the finite nature of the measuring instrument. As a crude example, measurements of the heights of trees would be compromised if our measuring stick was only 20 meters in length, because there are trees that are much taller than 20 meters. Here, 20 meters is the ceiling. Ceiling effects present statistical problems similar to those of "floor effect". Specifically, the utility of a measurement strategy is compromised by a lack of variability. In the case of a ceiling effect, the majority of scores are at or near the maximum possible for the test or measurement (in the example, we would observe a large clumping of tree heights at or near 20 meters, because the heights of trees taller than that would be credited with the 20 meter maximum score). |