A correction model for differences in the sample compositions: the degree of comparability as a function of age and schooling

Large-scale Assessments in Education

An IERI – International Educational Research Institute Journal

Table 3 Differences in the sample compositions and the unadjusted and adjusted scores

		(1)	(2)	(3)	(4)	(5)	(6)	(7)
		Difference to reference group (grade = 4/age = 10/test month = 5)			Raw and Adjusted Reading Scores
Study	Country	Diff. age (in years)	Diff. grade (in years)	Diff. test (in months)	Raw score common IRT scale	Adjusted score I β = 30 γ = 20	Adjusted score II β = 25 γ = 25	Adjusted score III β = 20 =30
1970 RCS	Hungary	0.58	0.29	no data available	471	448	449	451
	Italy	0.58	0.96		537	500	498	497
	Sweden	0.42	−0.47		536	533	537	542
	USA	0.58	0.65		496	466	465	465
1991 RLS	Hungary	−0.67	−1.00	no data available	445	485	487	488
	Italy	−0.17	0.00		490	495	494	493
	Sweden	−0.25	−1.00		506	534	537	541
	USA	0.00	0.00		514	514	514	514
2001 RLS	Hungary	−0.33	−1.00	0.00	465	495	498	502
	Italy	−0.17	0.00	0.02	503	508	507	506
	Sweden	−0.17	−1.00	−1.00	471	498	503	507
	USA	0.00	0.00	−0.38	506	507	507	507
2001 PIRLS	Hungary	0.67	0.00	0.00	506	486	489	493
	Italy	−0.17	0.00	0.00	501	506	505	504
	Sweden (G4*)	0.83	0.00	−2.00	524	503	508	513
	Sweden (G3*)	−0.17	−1.00	−2.00	470	499	504	509
	USA	0.25	0.00	−0.37	502	495	497	498
2006 PIRLS	Hungary	0.67	0.00	−1.01	510	492	496	500
	Italy	−0.33	0.00	−1.00	513	525	524	523
	Sweden	0.83	0.00	−0.66	509	485	490	494
	USA	0.08	0.00	−2.45	499	501	503	505