Formula of the form y ~ x +
cluster(w), where y is a continuous response, x is a
factor with two levels of treatment, and w is a factor
indicating the clusters.
data
Data frame
compare
Text vector stating the factor levels -
compare[1] is the control or reference group to
which compare[2] is compared
x
Trinomial vector $\{\Sigma I(xy)\}$
alpha
Complement of the confidence level.
df
Degrees of freedom. Default N-2
tdist
Use quantiles of t or Gaussian distribution
for confidence interval? Default t distribution.