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zinterval()

Usage:
zinterval(x[,y],cover:fraction,var:variance,[upper:T or lower:T])



Keywords: probabilities, descriptive statistics, comparisons
zinterval() computes a z-confidence interval for a population mean
or difference of population means, depending on whether one or two
variables are given as arguments.  By default, zinterval() 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 specify the
variance via var:variance.  For a two-sample interval, you may specify
different variances by using a vector of length two.

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 2005-08-12