************************************************************************ * * DAY 3 * * Orthogonal regression * ************************************************************************ use "E:\KURSER\Målemetoder\DAY 3\example7.dta", clear * Make data "long" rename y1 x3 rename y2 x4 reshape long x, i(no) j(ix) * Note: ix=1,2 for EMIT and ix=3,4 for FIA * We know already, that Measurement error (EMIT) > Measurement error (FIA), therefore * generate emit=1 for EMIT and emit=0 for FIA generate emit=(ix<3) label define emit 0 "EMIT" 1 "FIA" label values emit emit generate xxx=_n ************************************************************************ * Version 1 * Treat patients as fixed effects ************************************************************************ * Unequal measurement errors xi: xtmixed x i.emit*i.no || xxx: emit, nocons var nofetable scalar ll_unequal=e(ll) * Equal measurement errors, remember to drop the "nocons" xi: xtmixed x i.emit*i.no, var nofetable scalar ll_equal=e(ll) * Compute X2-test to compare measurement error display " Patient (no) as fixed effets : log-likelihood " _newline /// " equal measurement error " ll_equal _newline /// " unequal measurement error " ll_unequal _newline display " test equal measurement error" _newline /// " chi 2 " 2*(ll_unequal-ll_equal) /// " p-value " 1-chi2(1,2*(ll_unequal-ll_equal) ) ************************************************************************ * Version 2 * Treat patients as random effects ************************************************************************ * Unequal measurement errors xi: xtmixed x i.emit || no: || xxx: emit, nocons var nofetable scalar ll_unequal=e(ll) * Equal measurement errors, remember to drop the "nocons" xi: xtmixed x i.emit || no: , var nofetable scalar ll_equal=e(ll) * Compute X2-test to compare measurement error display " Patient (no) as random effets : log-likelihood " _newline /// " equal measurement error " ll_equal _newline /// " unequal measurement error " ll_unequal _newline display " test equal measurement error" _newline /// " chi 2 " 2*(ll_unequal-ll_equal) /// " p-value " 1-chi2(1,2*(ll_unequal-ll_equal) )