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tinterval()

Usage:
tinterval(x[,y],cover:fraction,[upper:T or lower:T, pool:T|F])



Keywords: probabilities, descriptive statistics, comparisons
tinterval() computes a t-confidence interval for a population mean
or difference of population means, depending on whether one or two
variables are given as arguments.  By default, tinterval() computes
a two-sided interval, but you may choose one-sided alternatives
by using one of lowerb:T or upperb:T.

You specify the coverage rate via cover:value. You may choose pooled
or unpooled variances in two-sample tests via pool:T or pool:F.

The output is a vector containing the estimate and interval bounds.

Because the variance of the data must be known, these intervals are
rarely used in practical data analysis.


Gary Oehlert 2006-01-30