caitalloc {SeqAlloc}

Sequential Allocation for CAIT Method

Description

Performs the sequential allocation for the covariate-adjusted-imbalance-tolerance (CAIT) method of allocating observations in a randomized experiment.

Usage

caitalloc(carwt_x1, p, tol)

Arguments

carwt_x1

matrix of dimension n x n, where n is the number of units to be randomly assigned to treatments. The (i,j) element of the matrix is the weighted match score of unit i and unit j. The matrix should be symmetric with diagonal elements of 1.

p

probability the next unit should be allocated to the experiment arm that currently has fewer observations.

tol

imbalance tolerance for deviation from equal allocation.

Value

Vector with the allocation to treatment (denoted by 1) and control (denoted by 0)

Note

This function works for categorical as well as binary covariates. The matrix carwt_x1 can be created from an X matrix by using the function weight_x in this package.

Author(s)

Xiaoshu Zhu [e-mail] and Sharon Lohr

References

Pocock, S.J. and R. Simon (1975). Sequential Treatment Assignment with Balancing for Prognostic Factors in a Controlled Clinical Trial. Biometrics 31, 103-115.

Lohr, S. and X. Zhu (2015). Randomized Sequential Individual Assignment in Social Experiments: Evaluating the Design Options Prospectively. Sociological Methods and Research. [Advance online publication: December 27, 2015] doi: 10.1177/0049124115621332.

See Also

weight_x

Examples

wtmat <- matrix(runif(10000), ncol=100) 
wtmat <- (wtmat * lower.tri(wtmat)) + t(wtmat * lower.tri(wtmat)) 
diag(wtmat) <- 1 

caitalloc(wtmat,1,3)