Table 1.

Importance of litter effects on body weight and behavioural tests

Variable	Reduction in $${\sigma }_{\epsilon }^2$$	P-value
Locomotor activity	61%	<0.001
Body weight	50%	0.003
Marbles buried	38%	0.045
Anxiety (open field)	35%	0.0504
Grooming	23%	0.116

The p-value tests whether the litter-to-litter variation was significantly greater than zero.

$${\sigma }_{\epsilon }^2$$

is the residual (unexplained) variation.