a.pes: One or Two-tailed p-value from ANCOVA to Effect Size
Description
Converts a one or two-tailed p-value from ANCOVA to an effect size of $d$ (mean difference), $g$ (unbiased estimate of $d$), $r$ (correlation coefficient), $z'$ (Fisher's $z$), and log odds ratio. The variances of these estimates are also computed.Usage
a.pes(p, n.1, n.2, R, q, tail = "two")
Arguments
p
One-tailed p-value reported in primary study.
n.1
Treatment group sample size.
n.2
Comparison group sample size.
R
Covariate outcome correlation or multiple correlation.
tail
One or two-tailed p-value. Default is two.
Value
- dStandardized mean difference ($d$).
- var.dVariance of $d$.
- gUnbiased estimate of $d$.
- var.gVariance of $g$.
- rCorrelation coefficient.
- var.rVariance of $r$.
- log.oddsLog odds ratio.
- var.log.oddsVariance of log odds ratio.
- nTotal sample size.
References
Borenstein (2009). Effect sizes for continuous data. In H. Cooper, L. V. Hedges, & J. C. Valentine (Eds.), The handbook of research synthesis and meta analysis (pp. 279-293). New York: Russell Sage Foundation.