quantitative methods
DESCRIPTION
Quantitative Methods. Combining continuous and categorical variables. Combining categorical and continuous variables. Reprise of models fitted so far. YIELD=FERTIL YIELDM=VARIETY VOLUME=HEIGHT MATHS=ESSAYS SPECIES2=SPECIES1 AMA=YEARS+HGHT FINALHT=INITHT+WATER WGHT=RLEG+LLEG - PowerPoint PPT PresentationTRANSCRIPT
Combining categorical and continuous variables
Reprise of models fitted so far
YIELD=FERTILYIELDM=VARIETY
VOLUME=HEIGHTMATHS=ESSAYSSPECIES2=SPECIES1
AMA=YEARS+HGHTFINALHT=INITHT+WATER
WGHT=RLEG+LLEGPOETSAGE=BYEAR+DYEARLVOLUME=LDIAM+LHGHT
YIELD=BLOCK+BEANSEEDS=COLUMN+ROW+TREATMT
Combining categorical and continuous variables
Reprise of models fitted so far
YIELD=FERTILYIELDM=VARIETY
VOLUME=HEIGHTMATHS=ESSAYSSPECIES2=SPECIES1
AMA=YEARS+HGHTFINALHT=INITHT+WATER
WGHT=RLEG+LLEGPOETSAGE=BYEAR+DYEARLVOLUME=LDIAM+LHGHT
YIELD=BLOCK+BEANSEEDS=COLUMN+ROW+TREATMT
ANOVA table - whether x-variables predict y-variable
Coefficients table - how x-variables predict y-variable
Combining categorical and continuous variables
Model formulae, model and fitted values
BACAFTER = BACBEF+TREATMNT
TREATMNT Coef 1 1
BACAFTER = + BACBEF + 2 2 + 3 -1 -2
TREATMNT CoefPREDICTED 1 -1.590BACAFTER = -0.013 + 0.8831BACBEF + 2 -0.726 3 2.316
(Model Formula)
(Model)
(Fitted Value Equation or Best Fit Equation)
Combining categorical and continuous variables
FAT = + *WEIGHT
FAT = + SEX Coeff M F -
FAT = + SEX Coeff + *WEIGHT M F -
Graphs and equations
Combining categorical and continuous variables
Orthogonality
… is a relationship that may hold between two x-variables
The general concept is that two x-variables are orthogonal if you can’t predict one when you know the other.
Combining categorical and continuous variables
Last words…
Next week: Interactions - getting more complex
Read Chapter 7 (a long one)
• Continuous and categorical variables can be freely combined in a model formula
• Know how to construct the model• Know how to construct the fitted value equation• Some variables may be treated in either way• The GLM encompasses many traditional tests