Floor effect explained

In statistics, a floor effect (also known as a basement effect) arises when a data-gathering instrument has a lower limit to the data values it can reliably specify.^[1] This lower limit is known as the "floor".^[2] The "floor effect" is one type of scale attenuation effect;^[3] the other scale attenuation effect is the "ceiling effect". Floor effects are occasionally encountered in psychological testing, when a test designed to estimate some psychological trait has a minimum standard score that may not distinguish some test-takers who differ in their responses on the test item content.^[4] Giving preschool children an IQ test designed for adults would likely show many of the test-takers with scores near the lowest standard score for adult test-takers (IQ 40 on most tests that were currently normed as of 2010). To indicate differences in current intellectual functioning among young children, IQ tests^[5] specifically for young children are developed, on which many test-takers can score well above the floor score. An IQ test designed to help assess intellectually disabled persons might intentionally be designed with easier item content and a lower floor score to better distinguish among individuals taking the test as part of an assessment process.^[6]

See also

• Ceiling effect (statistics)

Further reading

• Everitt, B.S. (2002) The Cambridge dictionary of Statistics, Second Edition. CUP.
• Book: Handbook of Intelligence . limited . Sternberg . Robert J. . Robert Sternberg . 456 . 2000 . Cambridge University Press . Cambridge . 978-0-521-59648-0.
• Book: WAIS-IV Clinical Use and Interpretation: Scientist-Practitioner Perspectives . limited . Weiss . Lawrence G. . Saklofske . Donald H. . Coalson . Diane . Raiford . Susan . 8 . Alan S. Kaufman (Foreword) . 2010 . Academic Press . Amsterdam . Practical Resources for the Mental Health Professional . 978-0-12-375035-8.
• Book: Groth-Marnat, Gary . Handbook of Psychological Assessment . 2009 . Wiley . Hoboken (NJ) . 978-0-470-08358-1 . Fifth.

Notes and References

1. Lim. Christopher R.. Harris. Kristina. Dawson. Jill. Beard. David J.. Fitzpatrick. Ray. Price. Andrew J.. 2015-07-01. Floor and ceiling effects in the OHS: an analysis of the NHS PROMs data set. BMJ Open. en. 5. 7. e007765. 10.1136/bmjopen-2015-007765. 2044-6055. 26216152. 4521553.
2. Web site: Floor Effect / Basement Effect: Definition. Stephanie. 2017-09-10. Statistics How To. en-US. 2020-04-14.
3. Web site: Scale Attenuation Effect - SAGE Research Methods. 2020-10-22. methods.sagepub.com. en.
4. Zhu. Leina. Gonzalez. Jorge. 2017. Modeling Floor Effects in Standardized Vocabulary Test Scores in a Sample of Low SES Hispanic Preschool Children under the Multilevel Structural Equation Modeling Framework. Frontiers in Psychology. en. 8. 2146. 10.3389/fpsyg.2017.02146. 29312033. 5732956. 1664-1078. free.
5. Sansone. Stephanie M. Schneider. Andrea. Bickel. Erika. Berry-Kravis. Elizabeth. Prescott. Christina. Hessl. David. 2014. Improving IQ measurement in intellectual disabilities using true deviation from population norms. Journal of Neurodevelopmental Disorders. 6. 1. 16. 10.1186/1866-1955-6-16. 1866-1947. 4613563. 26491488 . free .
6. Web site: IQ testing in individuals with intellectual disability. health.ucdavis.edu. 2020-04-14.