https://webpower.psychstat.org/wiki/ 2026-04-15T05:49:03-0400 https://webpower.psychstat.org/wiki/ https://webpower.psychstat.org/wiki/lib/tpl/dokuwiki/images/favicon.ico text/html 2025-04-27T14:02:08-0400 Anonymous (anonymous@undisclosed.example.com) https://webpower.psychstat.org/wiki/effectsize/cohen_s_d?rev=1745776928&do=diff Cohen's d for independent two-sample design Calculator ---------- For studying the standardized group mean difference in an independent two-sample design, the most popular effect size measure is defined as $$ \delta = \frac{\mu_1 - \mu_2}{\sigma} $$ where $\mu_1$ and $\mu_2$ are the population means of the two groups and $\sigma$$$ d = \frac{\bar{y}_1 - \bar{y}_2}{\sqrt{\frac{(n_{1}-1)s_{1}^{2}+(n_{2}-1)s_{2}^{2}}{n_{1}+n_{2}-2}}} $$$n_1$$n_2$$\bar{y}_1$$\bar{y}_1$$s_1^2$$s_2^2$$\lambda… text/html 2024-09-19T12:24:59-0400 Anonymous (anonymous@undisclosed.example.com) https://webpower.psychstat.org/wiki/effectsize/cohensd?rev=1726763099&do=diff Cohen's d for independent two-sample design text/html 2025-04-27T14:21:07-0400 Anonymous (anonymous@undisclosed.example.com) https://webpower.psychstat.org/wiki/effectsize/hedge_s_g?rev=1745778067&do=diff Hedges' g for independent two-sample design ---------- In independent two-sample design, the most popular effect size measure is defined as $$ \delta = \frac{\mu_1 - \mu_2}{\sigma} $$ where $\mu_1$ and $\mu_2$ are the population means of the two population and $\sigma$ is the population standard deviation which is assumed to be the same for the two populations.$$ g = d\times \frac{\Gamma(m/2)}{\sqrt{(m/2)} \Gamma[(m-1)/2]} $$$m = n_1 + n_2 - 2$$g$$$ var(g) = \frac{m(1+\tilde{n} \delta^2)}… text/html 2024-09-19T12:24:59-0400 Anonymous (anonymous@undisclosed.example.com) https://webpower.psychstat.org/wiki/effectsize/paired-t-test?rev=1726763099&do=diff Effect size and confidence interval for paired-t-test We implemented the method by Algina, J., & Keselman, H. J. (2003). Approximate confidence intervals for effect sizes. Educational and Psychological Measurement, 63, 537-553. The sample effect size is calculated as $$ d = \frac{\bar{y}_1 - \bar{y}_2}{\sqrt{(s_1^2 + s_2^2)/2}} $$$\bar{y}_1$$\bar{y}_1$$s_1^2$$s_2^2$$\lambda_L$$\lambda_U$$$\lambda_L = t^{-1}_{ncp}(t, df=n-1, 1-\alpha/2)$$$$\lambda_U = t^{-1}_{ncp}(t, df=n-1, \alpha/2)$$$$ t = \… text/html 2025-04-27T13:34:15-0400 Anonymous (anonymous@undisclosed.example.com) https://webpower.psychstat.org/wiki/effectsize/two-sample-t-test?rev=1745775255&do=diff Effect size and confidence interval for independent two-sample t-test ---------- Calculator ---------- How to use To use the calculator, information is needed according to whether you are using the raw data or summary statistics. When summary statistics are available $$ d = \frac{\bar{y}_1 - \bar{y}_2}{\sqrt{\frac{(n_{1}-1)s_{1}^{2}+(n_{2}-1)s_{2}^{2}}{n_{1}+n_{2}-2}}} $$$n_1$$n_2$$\bar{y}_1$$\bar{y}_1$$s_1^2$$s_2^2$$$ g = d\times \frac{\Gamma(m/2)}{\sqrt{(m/2)} \Gamma[(m-1)/2]} $$$m = n…