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Thread: GLM Shows Significance But Decision Tree Unable to Predict?

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    GLM Shows Significance But Decision Tree Unable to Predict?



    I'm trying to predict brand preference based on a number of attributes.

    General Linear Model shows that all but one attribute has a significance of < 0.05, so one might expect I'd have a good ability to predict brand selection.

    But running a Decision Tree shows that the correct brand is predicted only 25.7% of the the time.

    What am I missing?

    Thanks very much in advance to all for any info!

    Code: 
    * Generalized Linear Models.
    GENLIN BRAND_ID WITH Attribute_1 Attribute_2 Attribute_3 Attribute_4 Attribute_5 Attribute_6 
    Attribute_7 Attribute_8 Attribute_9
    /MODEL Attribute_1 Attribute_2 Attribute_3 Attribute_4 Attribute_5 Attribute_6 Attribute_7 
    Attribute_8 Attribute_9 INTERCEPT=YES
    DISTRIBUTION=POISSON LINK=LOG
    /CRITERIA METHOD=FISHER(1) SCALE=1 COVB=MODEL MAXITERATIONS=100 MAXSTEPHALVING=5 
    PCONVERGE=1E-006(ABSOLUTE) SINGULAR=1E-012 ANALYSISTYPE=3(WALD) CILEVEL=95 CITYPE=WALD 
    LIKELIHOOD=FULL
    /MISSING CLASSMISSING=EXCLUDE
    /PRINT CPS DESCRIPTIVES MODELINFO FIT SUMMARY SOLUTION.
    
    * Decision Tree.
    TREE BRAND_ID [n] BY Attribute_1 [s] Attribute_2 [s] Attribute_3 [s] Attribute_4 [s] Attribute_5 
    [s] Attribute_6 [s] Attribute_7 [s] Attribute_8 [s] Attribute_9 [s] 
    /TREE DISPLAY=TOPDOWN NODES=STATISTICS BRANCHSTATISTICS=YES NODEDEFS=YES SCALE=AUTO
    /DEPCATEGORIES USEVALUES=VALID
    /PRINT MODELSUMMARY CLASSIFICATION RISK
    /METHOD TYPE=CRT MAXSURROGATES=AUTO PRUNE=SE(1)
    /GROWTHLIMIT MAXDEPTH=AUTO MINPARENTSIZE=100 MINCHILDSIZE=50
    /VALIDATION TYPE=NONE OUTPUT=BOTHSAMPLES
    /CRT IMPURITY=GINI MINIMPROVEMENT=0.0001
    /COSTS EQUAL
    /PRIORS FROMDATA ADJUST=NO.
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