size.test.lc.ancova

Computes the sample size for each group (assuming equal sample sizes) required
to test a linear contrast of population means in an ANCOVA model with desired
power. In a nonexperimental design, the sample size is affected by the magnitude
of covariate mean differences across groups. The covariate mean differences can
be approximated by specifying the largest standardized covariate mean difference
across all pairwise comparisons and for all covariates. In an experiment, this
standardized mean difference is set to 0. 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.test.lc.ancova function

<dl><dt>alpha</dt>
<dd>alpha level for hypothesis test</dd>
<dt>pow</dt>
<dd>desired power</dd>
<dt>evar</dt>
<dd>planning value of within-group (error) variance</dd>
<dt>es</dt>
<dd>planning value of linear contrast</dd>
<dt>s</dt>
<dd>number of covariates</dd>
<dt>d</dt>
<dd>largest standardized mean difference for all covariates</dd>
<dt>v</dt>
<dd>vector of between-subjects contrast coefficients</dd></dl>

Arguments

Sample size for a mean linear contrast test in an ANCOVA — size.test.lc.ancova

<dl>

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


<dt>pow</dt>
<dd>desired power</dd>


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


<dt>es</dt>
<dd>planning value of linear contrast</dd>


<dt>s</dt>
<dd>number of covariates</dd>


<dt>d</dt>
<dd>largest standardized mean difference for all covariates</dd>


<dt>v</dt>
<dd>vector of between-subjects contrast coefficients</dd>

</dl>

size.test.lc.ancova: Sample size for a mean linear contrast test in an ANCOVA

Description

Usage

Value

Arguments

Examples