In statistics, the term floor effect refers to when data cannot take on a value lower than some particular number, called the floor.
An example of this is when an IQ test is given to young children who have either (a) been given training or (b) have been given no training. If the test is too difficult (so difficult that no amount of training will affect the ability to carry out the test), both group (a) and group (b) will perform particularly badly. This does not necessarily lead to the conclusion that the training has no effect on the ability to complete the IQ test. In fact, this may lead to a Type II error. The IQ test is too difficult, and by making the questions less difficult, training may have an effect on the ability to complete the IQ score.
Here, the floor effect is the data all hitting the bottom end of the distribution due to the extreme difficulty of the task. A ceiling effect is precisely the opposite - all participants reaching the high end of the distribution (e.g. the test was too easy).
Famous quotes containing the words floor and/or effect:
“Four and twenty at her back
And they were a’ clad out in green;
Tho the King of Scotland had been there
The warst o’ them might hae been his Queen.
On we lap and awa we rade
Till we cam to yon bonny ha’
Whare the roof was o’ the beaten gold
And the floor was o’ the cristal a’.”
—Unknown. The Wee Wee Man (l. 21–28)
“In his very rejection of art Walt Whitman is an artist. He tried to produce a certain effect by certain means and he succeeded.... He stands apart, and the chief value of his work is in its prophecy, not in its performance. He has begun a prelude to larger themes. He is the herald to a new era. As a man he is the precursor of a fresh type. He is a factor in the heroic and spiritual evolution of the human being. If Poetry has passed him by, Philosophy will take note of him.”
—Oscar Wilde (1854–1900)