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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/meta.ttestBF.R
\name{meta.ttestBF}
\alias{meta.ttestBF}
\title{Function for Bayesian analysis of one- and two-sample designs}
\usage{
meta.ttestBF(
t,
n1,
n2 = NULL,
nullInterval = NULL,
rscale = "medium",
posterior = FALSE,
callback = function(...) as.integer(0),
...
)
}
\arguments{
\item{t}{a vector of t statistics}
\item{n1}{a vector of sample sizes for the first (or only) condition}
\item{n2}{a vector of sample sizes. If \code{NULL}, a one-sample design is assumed}
\item{nullInterval}{optional vector of length 2 containing lower and upper bounds of
an interval hypothesis to test, in standardized units}
\item{rscale}{prior scale. A number of preset values can be given as
strings; see Details.}
\item{posterior}{if \code{TRUE}, return samples from the posterior instead
of Bayes factor}
\item{callback}{callback function for third-party interfaces}
\item{...}{further arguments to be passed to or from methods.}
}
\value{
If \code{posterior} is \code{FALSE}, an object of class
\code{BFBayesFactor} containing the computed model comparisons is
returned. If \code{nullInterval} is defined, then two Bayes factors will
be computed: The Bayes factor for the interval against the null hypothesis
that the standardized effect is 0, and the corresponding Bayes factor for
the compliment of the interval.
If \code{posterior} is \code{TRUE}, an object of class \code{BFmcmc},
containing MCMC samples from the posterior is returned.
}
\description{
This function computes mata-analytic Bayes factors, or samples from the posterior, for
one- and two-sample designs where multiple t values have been observed.
}
\details{
The Bayes factor provided by \code{meta.ttestBF} tests the null hypothesis that
the true effect size (or alternatively, the noncentrality parameters) underlying a
set of t statistics is 0. Specifically, the Bayes factor compares two
hypotheses: that the standardized effect size is 0, or that the standardized
effect size is not 0. Note that there is assumed to be a single, common effect size
\eqn{\delta}{delta} underlying all t statistics. For one-sample tests, the standardized effect size is
\eqn{(\mu-\mu_0)/\sigma}{(mu-mu0)/sigma}; for two sample tests, the
standardized effect size is \eqn{(\mu_2-\mu_1)/\sigma}{(mu2-mu1)/sigma}.
A Cauchy prior is placed on the standardized effect size.
The \code{rscale} argument controls the scale of the prior distribution,
with \code{rscale=1} yielding a standard Cauchy prior. See the help for
\code{\link{ttestBF}} and the references below for more details.
The Bayes factor is computed via Gaussian quadrature. Posterior samples are
drawn via independent-candidate Metropolis-Hastings.
}
\note{
To obtain the same Bayes factors as Rouder and Morey (2011),
change the prior scale to 1.
}
\examples{
## Bem's (2010) data (see Rouder & Morey, 2011)
t=c(-.15,2.39,2.42,2.43)
N=c(100,150,97,99)
## Using rscale=1 and one-sided test to be
## consistent with Rouder & Morey (2011)
bf = meta.ttestBF(t, N, rscale=1, nullInterval=c(0, Inf))
bf[1]
## plot posterior distribution of delta, assuming alternative
## turn off progress bar for example
samples = posterior(bf[1], iterations = 1000, progress = FALSE)
## Note that posterior() respects the nullInterval
plot(samples)
summary(samples)
}
\references{
Morey, R. D. & Rouder, J. N. (2011). Bayes Factor Approaches for Testing
Interval Null Hypotheses. Psychological Methods, 16, 406-419
Rouder, J. N., Speckman, P. L., Sun, D., Morey, R. D., & Iverson, G.
(2009). Bayesian t-tests for accepting and rejecting the null hypothesis.
Psychonomic Bulletin & Review, 16, 225-237
Rouder, J. N. & Morey, R. D. (2011). A Bayes Factor Meta-Analysis of Bem's ESP Claim.
Psychonomic Bulletin & Review, 18, 682-689
}
\seealso{
\code{\link{ttestBF}}
}
\author{
Richard D. Morey (\email{richarddmorey@gmail.com})
}
\keyword{htest}
|
