To install and load the library
install.packages("PowerUpR")
library(PowerUpR)Statistical power, minimum detectable effect size (MDES), MDES
difference (MDESD), or minimum required sample size (MRSS) can be
requested by using the relevant function given design parameters. In
general, each function begins with an output name,
follows by a period, and ends with a design name in the
form <output>.<design>(). There are three types
of output; mdes for main effects (mdes or
mdesd for moderation effects), power, and
mrss. Each output can be requested for eighteen types of
designs to detect main treatment effect; ira,
ira_pn, bira2, bira2_pn,
bira2f1, bira2c1, cra2,
cra2_pn, bira3, bcra3r2,
bcra3r2_pn, bcra3f2, cra3,
bira4, bcra4r2, bcra4r3,
bcra4f3, cra4, and seven types of designs to
detect moderator effects; mod211, mod212,
mod221, mod222, mod331,
mod332, and mod333. To detect mediator
effects, only power can be requested for seven types of
designs; med211, med221, med331,
med321, med311, med_pn21,
med_pn31, and med_pn32.
For designs to detect main effects, first three letters stand for the
type of assignment; for individual random assignment ira,
for blocked individual random assignment bira, for cluster
random assignment cra, and for blocked cluster random
assignment bcra. First (or the only number) indicate total
number of levels. The single letter inbetween refers to whether the top
level is random or fixed. Partially nested designs are denoted with
pn.
Naming conventions are slighlty different for designs to detect
moderator and mediator effects. Numbers following mod
keyword indicate total number of levels, the level at which
randomization takes place, and the level at which moderator resides
correspondingly. As for the mediator effects, numbers following
med keyword indicate the level at which treatment, mediator
and outcome variables reside.
For example, the function mdes.cra2() can be called to
calculate MDES for the main treatment effect in a two-level
cluster-randomized trial. Similiarly, the function
mdesd.mod222() can be called to calculate MDESD for
moderator effect residing at level 2 in a two-level cluster-randomized
trial. Finally, the function power.med221() can be called
to calculate statistical power for mediator residing at level 2 in a
two-level cluster-randomized trial.
Live app at:
https://powerupr.shinyapps.io/index/
Acknowledgement:
This work is supported by National Science Foundation through a collaborative research grant titiled “Power Analyses for Moderator and Mediator Effects in Cluster Randomized Trials” to Benjamin Kelcey (Award Number: 1437679), Jessaca Spybrook (Award Number:1437692), and Nianbo Dong (Award Number: 1437745).