Subject-by-Formulation Interaction
The S x F interaction is a measure of the extent to which the individual mean differences, mTj - mRj, between the T and R products are likely to differ.
sD2 = variance of (µTj - µRj)
= (sBT - sBR)2 + 2 (1- ?) sBT sBR
- µTj, µRj : individual-specific means
- sBT, sBR : between-subject standard deviations
- ? : correlation coefficient between µTj & µRj
- sD2 : S x F interaction variance component
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