Table 2. Model-implied covariance matrix.

Rows and columns correspond to the four measurement occasions (brain scans) distributed over two days. Parameters of the covariance matrix are the individual differences of the construct of interest, ${\displaystyle {\sigma }_T^2}$, the session-specific error variance, ${\displaystyle {\sigma }_S^2}$, the day-specific error variance, ${\displaystyle {\sigma }_D^2}$, and the residual error variance, ${\displaystyle {\sigma }_E^2}$.

	Scan 1	Scan 2	Scan 3	Scan 4
Scan 1	${\sigma }_T^2+{\sigma }_E^2+{\sigma }_D^2+{\sigma }_S^2$	${\sigma }_T^2+{\sigma }_D^2+{\sigma }_S^2$	${\sigma }_T^2$	${\sigma }_T^2$
Scan 2	${\sigma }_T^2+{\sigma }_D^2+{\sigma }_S^2$	${\sigma }_T^2+{\sigma }_E^2+{\sigma }_D^2+{\sigma }_S^2$	${\sigma }_T^2$	${\sigma }_T^2$
Scan 3	${\sigma }_T^2$	${\sigma }_T^2$	${\sigma }_T^2+{\sigma }_E^2+{\sigma }_D^2+{\sigma }_S^2$	${\sigma }_T^2+{\sigma }_D^2$
Scan 4	${\sigma }_T^2$	${\sigma }_T^2$	${\sigma }_T^2+{\sigma }_D^2$	${\sigma }_T^2+{\sigma }_E^2+{\sigma }_D^2+{\sigma }_S^2$