size.ci.gen2

Computes the sample size required to estimate a difference in population
parameters with desired precision in a 2-group design using a standard
error for a parameter estimate from a prior or pilot study. This function
can be used with any type of parameter where the standard error of the
parameter estimate is a function of the square root of the sample size
(most parameter estimates have this property). This function also assumes
that the sampling distribution of the parameter estimate is approximately
normal in large samples. Set R = 1 for equal sample sizes.

Implements confidence interval and sample size methods that
are especially useful in psychological research. The methods can be
applied in 1-group, 2-group, paired-samples, and multiple-group designs
and to a variety of parameters including means, medians, proportions,
slopes, standardized mean differences, standardized linear contrasts
of means, plus several measures of correlation and association.
Confidence interval and sample size functions are given for single
parameters as well as differences, ratios, and linear contrasts of
parameters. The sample size functions can be used to approximate the
sample size needed to estimate a parameter or function of parameters
with desired confidence interval precision or to perform a variety of
hypothesis tests (directional two-sided, equivalence, superiority,
noninferiority) with desired power. For details see: Statistical Methods
for Psychologists, Volumes 1 – 4, <https://dgbonett.sites.ucsc.edu/>.

Douglas G. Bonett

statpsych

Statistical Methods for Psychologists

Robert J. Calin-Jageman

size.ci.gen2 function

<dl><dt>alpha</dt>
<dd>alpha level for hypothesis test</dd>
<dt>se</dt>
<dd>standard error of parameter estimate from prior/pilot study</dd>
<dt>n0</dt>
<dd>sample size of prior/pilot study</dd>
<dt>w</dt>
<dd>desired confidence interval width</dd>
<dt>R</dt>
<dd>n2/n1 ratio</dd></dl>

Arguments

Sample size for a confidence interval for the difference of any type of
parameter — size.ci.gen2

<dl>

<dt>alpha</dt>
<dd>alpha level for hypothesis test</dd>


<dt>se</dt>
<dd>standard error of parameter estimate from prior/pilot study</dd>


<dt>n0</dt>
<dd>sample size of prior/pilot study</dd>


<dt>w</dt>
<dd>desired confidence interval width</dd>


<dt>R</dt>
<dd>n2/n1 ratio</dd>

</dl>

size.ci.gen2: Sample size for a confidence interval for the difference of any type of parameter

Description

Usage

Value

Arguments

Examples