Table 3.

Percentage of variance explained by the factor solutions in Additional file 2

V1 3-FAC			V2 3-FAC			V12 average 3-FAC			V12 average 4-FAC
Rotation SS Loadings			Rotation SS Loadings			Rotation SS Loadings			Rotation SS Loadings
EV	% variance	Cum %var	EV	% variance	Cum %var	EV	% variance	Cum %var	EV	% variance	Cum %var
2.818	23.484	23.484	3.152	26.267	26.267	3.008	25.065	25.065	2.626	21.884	21.884
2.466	20.550	44.033	2.436	20.297	46.563	2.520	20.998	46.064	2.167	18.060	39.943
2.282	19.021	63.054	2.055	17.126	63.689	2.182	18.186	64.249	2.083	17.362	57.305
									1.744	14.531	71.836

EV = post-rotation eigenvalues; these are typically more evenly spread in their values than before rotation, Cum %var. = cumulative percentage of the variance explained by factor scores, ie by adding the current absolute percent variance explained to the previous

The first two fields show straightforward 3-factor solutions on the data from each visit separately but with scale values based on Visit 1 and 2 averaged data combined, making the scaling identical across all 4 fields although the data sources differ. In the last two fields, the item data themselves are averaged for the two visits, so both the 3- and 4-factor solutions proceed on this same averaged Visit 1 & 2 data. The main text, supported by Additional file 2 b explains why visit-averaged data and then the 3-factor solution are preferred