Table 2. Comparison of the observed and imputed data for those with Visual perception scores and KS3 Maths and English scores (n = 4512) and for children excluded from the analysis.

	Observedn	%	Imputedn	%	Excludedn	%	P-value*
Maternal education	4392		120		8183		<0.0001
CSE or less		14.9		21.9		23.1
Vocational		9.6		11.0		10.0
O level		39.3		38.0		32.1
A level		24.5		20.3		21.3
Degree		11.7		8.8		13.4
Social class	4200		312		7455		<0.0001
I		11.5		7.8		14.2
II		43.9		35.5		40.4
III NM		28.4		29.3		23.9
III M		11.5		17.7		14.7
IV		4.1		8.4		5.6
V		0.5		1.3		1.1
ICD	4512		0		10811		<0.0001
No		98.6				97.2
Yes		1.4				2.8
Visual problems	3356		1156		3939		0.023
No		97.9		96.1		97.1
Yes		2.1		3.9		2.9
Pre term	4512		0		10219		<0.0001
No		94.6				88.1
Yes		5.4				11.9
SCBU	4368		44		7954		0.108
No		93.3		91.4		92.7
Yes		6.7		8.6		7.3
IUGR	4375		137		9258		0.302
No		90.4		85.9		89.8
Yes		9.6		14.1		10.2
IQ: mean	3607	103.99	905	98.7	3811	104.3	0.085
KS2 maths: mean	4442	4.69	70	3.26	5757	4.34	<0.0001
KS2 reading: mean	4271	4.59	241	2.70	5559	4.25	<0.0001

*Comparing those included (observed) to those excluded.