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Published byJoanna Dorthy Maxwell Modified over 8 years ago
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Testing Significance of coefficients Usually, first examination of model Does the model including the independent variable provide significantly more information than a model without the variable?
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Compare two models Model containing x Null (Intercept only model)
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The null (intercept only) model proc freq data=s5238.chdage; tables chd; run; proc logistic data=s5238.chdage descending; model chd=; run;
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Simple Linear Regression title "Height and FEV in 12 boys, 10-15 years old"; data fev1ht; input height fev @@; label fev="Forced Expiratory Volume (liters)" height="Height (cm)"; datalines; 134 1.7 158 2.7 138 1.9 162 3.0 150 2.2 174 3.8 142 2.0 166 3.1 146 2.1 170 3.4 154 2.5 178 3.9 ; proc sql; select * from fev1ht order by height ; quit; title;
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Simple linear regression, proc reg proc reg data=fev1ht plots=none; model fev=height; quit;
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Two Equivalent Tests
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Two tests (no longer equivalent -- asymptotically equivalent) Wald Test Likelihood Ratio Test
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Wald Test (two equivalent versions)
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ods select parameterestimates; proc logistic data=s5238.chdage descending; model chd=age; run;
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The Likelihood Ratio Statistic Software usually report either log(likelihood) or -2log(Likelihood) SAS reports -2log(Likelihood) (deviance)
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ods select globaltests parameterestimates; proc logistic data=s5238.chdage ; model chd(event="1")=age; run;
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