Greenhouse–Geisser correction
The Greenhouse–Geisser correction is a statistical method of adjusting for lack of
The Greenhouse–Geisser correction is an estimate of sphericity (). If sphericity is met, then . If sphericity is not met, then epsilon will be less than 1 (and the degrees of freedom will be overestimated and the F-value will be inflated).[2] To correct for this inflation, multiply the Greenhouse–Geisser estimate of epsilon to the degrees of freedom used to calculate the F critical value.
An alternative correction that is believed to be less conservative is the Huynh–Feldt correction (1976). As a general rule of thumb, the Greenhouse–Geisser correction is the preferred correction method when the epsilon estimate is below 0.75. Otherwise, the Huynh–Feldt correction is preferred.[3]
See also
References
- ^ Greenhouse, S. W.; Geisser, S. (1959). "On methods in the analysis ofprofile data". Psychometrika. 24: 95–112.
- ISBN 978-1-84787-906-6.
- ISBN 978-1-119-05269-2.