ci.ratio.sd2

Computes a robust confidence interval for a ratio of population standard
deviations in a 2-group design. This function is a modification of the
confidence interval proposed by Bonett (2006). The original Bonett method
used a pooled kurtosis estimate in the standard error that assumed equal
variances, which limited the confidence interval's use to tests of equal
population variances and equivalence tests. This function uses a pooled
kurtosis estimate that does not assume equal variances and provides a
useful confidence interval for a ratio of standard deviations under general
conditions. This function requires of minimum sample size of four per
group but sample sizes of at least 10 per group are recommended.

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

ci.ratio.sd2 function

<dl><dt>alpha</dt>
<dd>alpha level for 1-alpha confidence</dd>
<dt>y1</dt>
<dd>vector of scores for group 1</dd>
<dt>y2</dt>
<dd>vector of scores for group 2</dd></dl>

Arguments

Confidence interval for a 2-group ratio of standard deviations — ci.ratio.sd2

<dl>

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


<dt>y1</dt>
<dd>vector of scores for group 1</dd>


<dt>y2</dt>
<dd>vector of scores for group 2</dd>

</dl>

ci.ratio.sd2: Confidence interval for a 2-group ratio of standard deviations

Description

Usage

Value

Arguments

References

Examples