# qqstats: QQ Summary Statistics In Matching: Multivariate and Propensity Score Matching with Balance Optimization

 qqstats R Documentation

## QQ Summary Statistics

### Description

This function calculates a set of summary statistics for the QQ plot of two samples of data. The summaries are useful for determining if the two samples are from the same distribution. If `standardize==TRUE`, the empirical CDF is used instead of the empirical-QQ plot. The later retains the scale of the variable.

### Usage

``````qqstats(x, y, standardize=TRUE, summary.func)
``````

### Arguments

 `x` The first sample. `y` The second sample. `standardize` A logical flag for whether the statistics should be standardized by the empirical cumulative distribution functions of the two samples. `summary.func` A user provided function to summarize the difference between the two distributions. The function should expect a vector of the differences as an argument and return summary statistic. For example, the `quantile` function is a legal function to pass in.

### Value

 `meandiff` The mean difference between the QQ plots of the two samples. `mediandiff` The median difference between the QQ plots of the two samples. `maxdiff` The maximum difference between the QQ plots of the two samples. `summarydiff` If the user provides a `summary.func`, the user requested summary difference is returned. `summary.func` If the user provides a `summary.func`, the function is returned.

### Author(s)

Jasjeet S. Sekhon, UC Berkeley, sekhon@berkeley.edu, https://www.jsekhon.com.

### References

Sekhon, Jasjeet S. 2011. "Multivariate and Propensity Score Matching Software with Automated Balance Optimization.” Journal of Statistical Software 42(7): 1-52. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.18637/jss.v042.i07")}

Diamond, Alexis and Jasjeet S. Sekhon. Forthcoming. "Genetic Matching for Estimating Causal Effects: A General Multivariate Matching Method for Achieving Balance in Observational Studies.” Review of Economics and Statistics. https://www.jsekhon.com

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

### Examples

``````#
# Replication of Dehejia and Wahba psid3 model
#
# Dehejia, Rajeev and Sadek Wahba. 1999.``Causal Effects in
# Non-Experimental Studies: Re-Evaluating the Evaluation of Training
# Programs.''Journal of the American Statistical Association 94 (448):
# 1053-1062.
#

data(lalonde)

#
# Estimate the propensity model
#
glm1  <- glm(treat~age + I(age^2) + educ + I(educ^2) + black +
hisp + married + nodegr + re74  + I(re74^2) + re75 + I(re75^2) +
u74 + u75, family=binomial, data=lalonde)

#
#save data objects
#
X  <- glm1\$fitted
Y  <- lalonde\$re78
Tr  <- lalonde\$treat

#
# one-to-one matching with replacement (the "M=1" option).
# Estimating the treatment effect on the treated (the "estimand" option which defaults to 0).
#
rr  <- Match(Y=Y,Tr=Tr,X=X,M=1);
summary(rr)

#
# Do we have balance on 1975 income after matching?
#
qqout  <- qqstats(lalonde\$re75[rr\$index.treated], lalonde\$re75[rr\$index.control])
print(qqout)
``````

Matching documentation built on Sept. 14, 2023, 5:08 p.m.