Still feeling my way around using R...
What I have done so far:
I have a data.frame 'results' with response 'Fail', and three factors
'PREP', 'CLEAN' & 'ADHES'. ADHES has 3 levels: Crest Cryst Poly
I calculated the variances:
sigma..k=tapply(Fail,ADHES,var)
print(sqrt(sigma..k)):
Crest Cryst Poly 17.56668 41.64679 39.42669
then used leveneTest to test for constance of variance:
print(leveneTest(Fail~ADHES))
Levene's Test for Homogeneity of Variance (center = median)
Df F value Pr(>F)
group 2 3.929 0.02588 *
51
The Question:
Now I want to use Levene's to test for constance of variance between only
the Cryst & Poly levels of the factor ADHES, but I cant work out the syntax
to do this in R.
Could anyone help, please?
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