pi.cronbach

Computes approximate one-sided or two-sided prediction limits for the
estimated Cronbach reliability in a future study with a planned sample
size of n. The prediction interval uses a Cronbach reliability estimate
from a prior study.
The size.ci.cronbach and size.ci.cronbach2 functions require a planning
value of the expected sample value of Cronbach's reliability in the
planned study. A one-sided lower prediction limit for the sample value
of Cronbach's reliability in the planned study can be used in the
size.ci.cronbach and size.ci.cronbach2 functions to obtain conservatively
large sample size requirements. This strategy for specifying a reliability
planning value is useful in applications where the population Cronbach
reliability in the prior study is assumed to be very similar to the
population Cronbach reliability in the planned study.

Implements confidence interval and sample size methods that are especially
useful in psychological research but are also useful in educational, social science,
business, and biological research. This package includes more than 100 confidence
interval functions and more than 80 sample size functions for 1-group, 2-group,
paired-samples, and multiple-group designs and for a variety of parameters including
means, medians, proportions, slopes, standardized mean differences, standardized
linear contrasts of means, and several measures of correlation and association. 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 about these methods 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

pi.cronbach function

<dl><dt>alpha</dt>
<dd>alpha value for 1-alpha confidence</dd>
<dt>rel</dt>
<dd>estimated Cronbach reliability from prior study</dd>
<dt>r</dt>
<dd>number of measurements (e.g., items, raters, etc.)</dd>
<dt>n0</dt>
<dd>sample size used to estimate reliability in prior study</dd>
<dt>n</dt>
<dd>planned sample size of future study</dd>
<dt>type</dt>
<dd><ul>
<li>set to 1 for two-sided prediction interval</li>
<li>set to 2 for one-sided upper prediction limit</li>
<li>set to 3 for one-sided lower prediction limit</li>
</ul></dd></dl>

Arguments

Prediction limits for sample value of Cronbach reliability in a future study — pi.cronbach

<dl>

<dt>alpha</dt>
<dd>alpha value for 1-alpha confidence</dd>


<dt>rel</dt>
<dd>estimated Cronbach reliability from prior study</dd>


<dt>r</dt>
<dd>number of measurements (e.g., items, raters, etc.)</dd>


<dt>n0</dt>
<dd>sample size used to estimate reliability in prior study</dd>


<dt>n</dt>
<dd>planned sample size of future study</dd>


<dt>type</dt>
<dd><ul>
<li>set to 1 for two-sided prediction interval</li>
<li>set to 2 for one-sided upper prediction limit</li>
<li>set to 3 for one-sided lower prediction limit</li>
</ul></dd>

</dl>

pi.cronbach: Prediction limits for sample value of Cronbach reliability in a future study

Description

Usage

Value

Arguments

Examples