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slope_1
2008 Oct 15
1
Parameter estimates from an ANCOVA
...raction
scatterplot(y~categ|cont) # shows effect of the categorical variable,
irrespective of cont
summary(fit); anova(fit)
coeff=coef(summary(fit))[,1] # column of estimates to "coeff"
grandmean=coeff[1]+ mean(cont)*coeff[3] #GM = intercept +
mean(cont)*regression_slope = 45.00677
slope_A=coeff[3]+coeff[4] #slope of individual regression for A = 3.998
slope_B=coeff[3]+(-coeff[4]) #slope of individual regression for B = 2.002
tapply(y, categ, mean) #these are what I want to get back out from the
parameter estimates
# in my world the parameter estimate should be cell mean(A) - gra...