size.ci.condmean

Computes the total sample size required to estimate a population conditional
mean of y at x = x* in a fixed-x linear regression model with desired
confidence interval precision. The total sample size would be allocated to
the levels of the quantitative factor, and it might be necessary to increase
the total sample size to give the desired sample size at each level of
the fixed factor. Set the error variance planning value to the largest value
within a plausible range for a conservatively large sample size.

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.condmean function

<dl><dt>alpha</dt>
<dd>alpha level for 1-alpha confidence</dd>
<dt>evar</dt>
<dd>planning value of within group (error) variance</dd>
<dt>xvar</dt>
<dd>variance of fixed predictor variable</dd>
<dt>diff</dt>
<dd>difference between x* and mean of x</dd>
<dt>w</dt>
<dd>desired confidence interval width</dd></dl>

Arguments

Sample size for a conditional mean confidence interval — size.ci.condmean

<dl>

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


<dt>evar</dt>
<dd>planning value of within group (error) variance</dd>


<dt>xvar</dt>
<dd>variance of fixed predictor variable</dd>


<dt>diff</dt>
<dd>difference between x* and mean of x</dd>


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

</dl>

size.ci.condmean: Sample size for a conditional mean confidence interval

Description

Usage

Value

Arguments

Examples