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propinterval()

Usage:
propinterval(x[,y],cover:fraction,[options])
propinterval(s1,n1[,s2,n2],cover:fraction,[options])
options can include upperb:T or lowerb:T, plus4:T|F.



Keywords: probabilities, descriptive statistics, comparisons
propinterval() computes a z-confidence interval for a population
proportion or difference of population proportions, depending on
whether data for one or two variables are given as arguments.  By
default, propinterval() computes a two-sided interval, but you may
choose one-sided alternatives by using one of lowerb:T or upperb:T.
Arguments may be either vectors of 0/1 data, or may be counts of
successes and numbers of trials.  

You specify the coverage rate via cover:value. 

You may specify the Agresti "add 4" procedure via plus4:T.  This
will add 2 successes and two failures (split among the two samples
for two-sample tests).

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


Gary Oehlert 2006-01-30