Table 4.

Model details and results of the multilevel modelling

			Fractional			Goodness of fit
			polynomial powers
Model specification	Detail	N	Median	SD	Deviance	Observations	Observations
						<3rd centile	>97th centile
Random intercept	Take the mean of the	20 030	2, 2	1	136 690	638 (3.2%)	647 (3.2%)
two‐level model	triplicate FHC
	measurements
	for each visit
Random intercept	Take the mean of the	20 030	2, 2	1	132 845	866 (4.3%)	923 (4.6%)
and slope	triplicate FHC
two‐level model	measurements
	for each visit
Random intercept	Randomly select	20 030	2, 2	1	135 710	926 (4.6%)	1009 (5.0%)
slope and	one of the three FHC
two‐level model	measurements
	for each visit
Random intercept	Consider all	59 973	2, 2	3, 3, 3	346 036	2993 (5.0%)	3231(5.4%)
and slope	three data levels
three‐level model