PowerUpR (version 0.1.3)

power.cra2r2: Model 3.1: Statistical Power Calculator for 2-Level Cluster Random Assignment Design, Treatment at Level 2

Description

power.cra2r2 calculates statistical power for designs with 2-levels where level 2 units are randomly assigned to treatment and control groups.

Usage

power.cra2r2(mdes=.25, alpha=.05, two.tail=TRUE,
               rho2,
               g2=0, P=.50, R12=0, R22=0,
               n, J, ...)

Arguments

mdes

minimum detectable effect size.

alpha

probability of type I error.

two.tail

logical; TRUE for two-tailed hypothesis testing, FALSE for one-tailed hypothesis testing.

rho2

proportion of variance in the outcome explained by level 2 units.

P

proportion of level 2 units randomly assigned to treatment.

g2

number of covariates at level 2.

R12

proportion of level 1 variance in the outcome explained by level 1 covariates.

R22

proportion of level 2 variance in the outcome explained by level 2 covariates.

n

harmonic mean of level 1 units across level 2 units (or simple average).

J

level 2 sample size.

...

to handle extra parameters passed from other functions, do not define any additional parameters.

Value

fun

function name.

par

list of parameters used in power calculation.

df

degrees of freedom

M

multiplier for MDES calcuation given degrees of freedom, \(\alpha\) and \(\beta\) (1-power).

power

statistical power (1 - type II error).

Details

Power formula was derived within power analysis framework descibed by Hedges & Rhoads (2009). Further definition of design parameters can be found in Dong & Maynard (2013).

References

Dong, N., & Maynard, R. A. (2013). PowerUp!: A Tool for Calculating Minum Detectable Effect Sizes and Minimum Required Sample Sizes for Experimental and Quasi-Experimental Design Studies,Journal of Research on Educational Effectiveness, 6(1), 24-6. Hedges, L. & Rhoads, C.(2009). Statistical Power Analysis in Education Research (NCSER 2010-3006). Washington, DC: National Center for Special Education Research, Institute of Education Sciences, U.S. Department of Education. This report is available on the IES website at http://ies.ed.gov/ncser/.

See Also

mdes.cra2r2, mrss.cra2r2, optimal.cra2r2

Examples

## Not run: ------------------------------------
# 
#    power.cra2r2(rho2=.20,
#                 n=4, J=20)
# 
#   
## ---------------------------------------------