pi.var

Computes a two-sided or one-sided prediction limit for the estimated
variance in a future study for a planned sample size. The prediction limit
uses a variance estimate from a prior study.
Several confidence interval sample size functions in this package require
a planning value of the estimated variance that is expected in the planned
study. A one-sided upper variance prediction limit is useful as a variance
planning value for the sample size required to obtain a confidence interval
with desired width. This strategy for specifying a variance planning value
is useful in applications where the population variance in the prior study
is assumed to be very similar to the population variance in the planned
study.

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

pi.var function

<dl><dt>alpha</dt>
<dd>alpha value for upper 1-alpha confidence</dd>
<dt>var</dt>
<dd>estimated variance from prior study</dd>
<dt>n0</dt>
<dd>sample size used to estimate variance</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 an estimated variance — pi.var

<dl>

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


<dt>var</dt>
<dd>estimated variance from prior study</dd>


<dt>n0</dt>
<dd>sample size used to estimate variance</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.var: Prediction limits for an estimated variance

Description

Usage

Value

Arguments

References

Examples