nearfar (version 1.3)

eff_ratio: Inference for effect ratio

Description

Conducts inference on effect ratio as described in Section 3.3 of Baiocchi (2010), resulting in an estimate and a permutation based confidence interval for the effect ratio.

Usage

eff_ratio(dta, match, outc, trt, alpha)

Value

est.emp

Empirical estimate of effect ratio

est.HL

Hodges-Lehmann type estimate of effect ratio

lower

Lower limit to 1-alpha/2 confidence interval for effect ratio

upper

Upper limit to 1-alpha/2 confidence interval for effect ratio

Arguments

dta

The name of the data frame object

match

Data frame where first column contains indices for those individuals encouraged into treatment by instrumental variable and second column contains indices for those individuals discouraged from treatment by instrumental variable; returned by both opt_nearfar and matches

outc

The name of the outcome variable in quotes, e.g., ``wages''

trt

The name of the treatment variable, e.g., ``educ''

alpha

Level of confidence interval

Author

Joseph Rigdon

References

Baiocchi M, Small D, Lorch S, Rosenbaum P (2010). Building a stronger instrument in an observational study of perinatal care for premature infants. Journal of the American Statistical Association, 105(492), 1285-1296.

Examples

k2 = matches(dta=mtcars, covs=c("cyl", "disp"), sinks=0.2, iv="carb",
    cutpoint=2, imp.var=c("cyl"), tol.var=0.03)

eff_ratio(dta=mtcars, match=k2, outc="wt", trt="gear", alpha=0.05)