% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/power.R
\name{mb_icc_reference}
\alias{mb_icc_reference}
\title{Reference intra-class correlation values}
\usage{
mb_icc_reference(domain = NULL)
}
\arguments{
\item{domain}{Optional character scalar. One of \code{"education"},
\code{"health"}, \code{"employment"}, \code{"local_government"},
\code{"criminal_justice"}, \code{"housing"}. If \code{NULL} (default),
returns the entire reference table.}
}
\value{
A data frame with columns \code{domain}, \code{outcome},
\code{unit_of_clustering}, \code{icc_low}, \code{icc_central}, \code{icc_high},
\code{value_source}, \code{source}, \code{notes}.
}
\description{
Returns bundled reference ICC values for common UK policy
domains and units of clustering. Use these for evaluation
planning when domain-specific baseline data are not available.
}
\details{
Values are \emph{reference} ICCs for planning purposes only.
Wherever feasible, evaluators should compute domain-specific
ICCs from baseline data before finalising sample size
calculations.

Each row carries a \code{value_source} flag:
\itemize{
\item \code{"table_quote"}: direct extraction of a specific row or value
from a published table (cited table number in the \code{source}
field).
\item \code{"central_estimate"}: researcher synthesis of a plausible
central value within the published range, used as a
practitioner default in the absence of domain-specific
baseline data.
}

At v0.1.0 every bundled row is \code{central_estimate}. Future
versions will upgrade individual rows to \code{table_quote} as exact
table-level citations are added. Treat the bundled values as a
planning prior; verify against your own baseline ICC before
relying on them in a published power calculation.
}
\examples{
mb_icc_reference()
mb_icc_reference("education")
}
\references{
Hedges, L. V., Hedberg, E. C. (2007). Educational Evaluation
and Policy Analysis 29(1).
\url{doi:10.3102/0162373707299706}.

Adams, G., Gulliford, M. C., Ukoumunne, O. C., Eldridge, S.,
Chinn, S., Campbell, M. J. (2004). Patterns of intra-cluster
correlation from primary care research. Statistics in
Medicine 23. \url{doi:10.1002/sim.1764}.

Campbell, M. K., Mollison, J., Grimshaw, J. M. (2000). Cluster
trials in implementation research: estimation of intracluster
correlation coefficients and sample size. BMJ 321.
\url{doi:10.1136/bmj.321.7263.778}.
}
\seealso{
\code{\link[=mb_cluster_design]{mb_cluster_design()}}, \code{\link[=mb_stepped_wedge]{mb_stepped_wedge()}}.

Other power: 
\code{\link{mb_cluster_design}()},
\code{\link{mb_mde}()},
\code{\link{mb_power}()},
\code{\link{mb_sample_size}()},
\code{\link{mb_stepped_wedge}()}
}
\concept{power}
