randomizr: Tools for random assignment and random sampling
randomizr is designed to make conducting field, lab, survey, or
online experiments easier by automating the random assignment process.
Social and lab scientists conducting experiments need a process to
assign individuals or units of observation to treatment or control
wings. Common designs include simple random assignment, complete
randomization, block randomization, cluster randomization, and blocked
cluster randomization. randomizr automates all of these processes
and assists scientists in doing transparent, replicable science. We
offer randomizr for both
R and
Stata.
Installing randomizr for R
Installing the latest stable version of randomizr in R:.
install.packages("randomizr")Getting started with randomizr for R
randomizr has five main random assignment functions, corresponding
to the common experimental designs listed above. You can read more about
using each of these functions in our reference
library or by
clicking on the function names: simple_ra(), complete_ra(),
block_ra(), cluster_ra(), and block_and_cluster_ra().
complete_ra() (Complete randomization) is the function that will be
most appropriate for a large number of experimental situations: when you
want to assign a fixed m units out of a population of N units to
treatment:
library(randomizr)
Z <- complete_ra(N = 100, m = 50)
table(Z)| 0 | 1 |
|---|---|
| 50 | 50 |
A more complicated design that, for example, assigns different numbers
of clusters to three different treatments, makes use of cluster_ra()
(Cluster randomization):
# This makes a cluster variable: one unit in cluster "a", two in "b"...
clust_var <- rep(letters[1:15], times = 1:15)
Z <- cluster_ra(
clusters = clust_var,
m_each = c(4, 4, 7),
conditions = c("control", "placebo", "treatment")
)
table(Z, clust_var)| a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| control | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 9 | 0 | 0 | 0 | 0 | 14 | 15 |
| placebo | 0 | 0 | 3 | 0 | 5 | 0 | 7 | 0 | 0 | 0 | 0 | 12 | 0 | 0 | 0 |
| treatment | 0 | 2 | 0 | 4 | 0 | 6 | 0 | 8 | 0 | 10 | 11 | 0 | 13 | 0 | 0 |
For more information about all of randomizr’s functionality, please see our online tutorial
randomizr for Stata
Installing the latest stable version of randomizr from ssc is easy:
ssc install randomizrIf you would like to install the latest development release directly from GitHub, run the following code:
net install randomizr, from(https://raw.githubusercontent.com/DeclareDesign/strandomizr/master/) replaceHappy randomizing!