What does a Huynh-Feldt estimate value of 1 indicate?

What does a Huynh-Feldt estimate value of 1 indicate?

• A. The data completely meet the sphericity assumption
• B. The data significantly violate sphericity
• C. The data are not suitable for MANOVA
• D. The sample size is insufficient

Answer: (A)

Sphericity and how the degrees of freedom are treated in repeated-measures ANOVA are being tested here. The Huynh-Feldt epsilon is an estimate of how much the sphericity assumption holds. It scales the degrees of freedom for the F-tests to control Type I error when sphericity is violated. An epsilon value of 1 means there is no departure from sphericity; the correction factor is 1, so the uncorrected degrees of freedom and the standard F-tests are appropriate. In other words, the data are compatible with sphericity, so you don’t need to adjust the results. If epsilon were less than 1, it would indicate some violation of sphericity and a correction would be advisable. The other statements—significant violation of sphericity, unsuitability for MANOVA, or insufficient sample size—do not follow from an HF value of 1.

Sphericity and how the degrees of freedom are treated in repeated-measures ANOVA are being tested here. The Huynh-Feldt epsilon is an estimate of how much the sphericity assumption holds. It scales the degrees of freedom for the F-tests to control Type I error when sphericity is violated. An epsilon value of 1 means there is no departure from sphericity; the correction factor is 1, so the uncorrected degrees of freedom and the standard F-tests are appropriate. In other words, the data are compatible with sphericity, so you don’t need to adjust the results.

If epsilon were less than 1, it would indicate some violation of sphericity and a correction would be advisable. The other statements—significant violation of sphericity, unsuitability for MANOVA, or insufficient sample size—do not follow from an HF value of 1.