balanceUV {Matching}R Documentation

Univariate Balance Tests

Description

This function provides a number of univariate balance tests. Generally, users should call MatchBalance and not this function directly.

Usage

balanceUV(Tr, Co, weights = rep(1, length(Co)), exact = FALSE, ks=FALSE,
          nboots = 1000, paired=TRUE, match=FALSE,
          weights.Tr=rep(1,length(Tr)), weights.Co=rep(1,length(Co)))

Arguments

Tr A vector containing the treatment observations.
Co A vector containing the control observations.
weights A vector containing the observation specific weights. Only use this option when the treatment and control observations are paired (as they are after matching).
exact A logical flag indicating if the exact Wilcoxon test should be used instead of the test with a correction. See wilcox.test for details.
ks A logical flag for if the univariate bootstrap Kolmogorov-Smirnov (KS) test should be calculated. If the ks option is set to true, the univariate KS test is calculated for all non-dichotomous variables. The bootstrap KS test is consistent even for non-continuous variables. See ks.boot for more details.
nboots The number of bootstrap samples to be run for the ks test. If zero, no bootstraps are done. Bootstrapping is highly recommended because the bootstrapped Kolmogorov-Smirnov test only provides correct coverage even for non-continuous covariates. At least 500 nboots (preferably 1000) are recommended for publication quality p-values.
paired A flag for if the paired t.test should be used.
match A flag for if the Tr and Co objects are the result of a call to Match.
weights.Tr A vector of weights for the treated observations.
weights.Co A vector of weights for the control observations.

Value

sdiff This is the standardized difference between the treated and control units. That is, the mean difference between treatment and control units divided by the pooled standard deviation.
mean.Tr The mean of the treatment group.
mean.Co The mean of the control group.
var.Tr The variance of the treatment group.
var.Co The variance of the control group.
p.value The p-value from the two-sided weighted t.test.
var.ratio var.Tr/var.Co.
ks The object returned by ks.boot.
tt The object returned by two-sided weighted t.test.

Author(s)

Jasjeet S. Sekhon, UC Berkeley, sekhon@berkeley.edu, http://sekhon.polisci.berkeley.edu/.

References

Hollander, Myles and Douglas A. Wolfe. 1973. Nonparametric statistical inference. New York: John Wiley & Sons.

Sekhon, Jasjeet S. 2004. ``Balance Tests for Matching Estimators.'' Working Paper. http://sekhon.polisci.berkeley.edu/matching

See Also

Also see summary.balanceUV, ks.boot, Match, GenMatch, MatchBalance, balanceMV, GerberGreenImai, lalonde

Examples

data(lalonde)
attach(lalonde)

foo  <- balanceUV(re75[treat==1],re75[treat!=1])
summary(foo)


[Package Matching version 1.8-6 Index]