/* ---------------------------------------------------------
	FILE: cfa.nmtwins.sas

	DATA: National Merit Twin data

	PURPOSE: Confirmatory factor analysis
  ---------------------------------------------------------- */

* - NOTE: Assign LIBNAME p7291 to the directory/folder
	containing the Natinoal Merit Twin data;
*LIBNAME p7291 '';

OPTIONS NOCENTER NODATE PAGENO=1;
TITLE  National Merit Twins;
TITLE2 Confirmatory Factor Analysis for NMSQT scales;
PROC CALIS DATA=p7291.nmtwins CORR PRINT;
	VAR English -- Vocab;
	LINEQS
		English = lam11 FVerbal + lam12 FQuant + e_Eng,
		Math    = lam21 FVerbal + lam22 FQuant + e_Math,
		SocSci  = lam31 FVerbal + lam32 FQuant + e_SS,
		NatSci  = lam41 FVerbal + lam42 FQuant + e_NS,
		Vocab   = lam51 FVerbal + lam52 FQuant + e_Voc;
	STD
		FVerbal = V_FVerbal,
		FQuant  = V_FQuant,
		e_Eng   = V_eEng,
		e_Math  = V_eMath,
		e_SS    = V_eSS,
		e_NS    = V_eNS,
		e_Voc   = V_eVoc;
	COV
		FVerbal FQuant = COV_FVerb _FQuant;
	* - constraints: set 1: constraints needed to identify the model;
		V_FVerbal = 1;
		V_FQuant  = 1;
	* - constraints: set 2: substantive constraints hypothesized
		by the theory that one factor will be a verbal factor and
		the other will be a quantitative factor;
		lam12 = 0;
		lam52 = 0;
		lam21 = 0;
RUN;