# Dependent Sample T-test: 1-tailed

** Large Effect Size**

Power analysis for a dependent sample *t*-test was conducted in G-POWER to determine a sufficient sample size using an alpha of 0.05, a power of 0.80, a large effect size (*dz* = 0.8), and one tail (Faul et al., 2008). Based on the aforementioned assumptions, the desired sample size is 12.

** Medium Effect Size**

Power analysis for a dependent sample *t*-test was conducted in G-POWER to determine a sufficient sample size using an alpha of 0.05, a power of 0.80, a medium effect size (*dz* = 0.5), and one tail (Faul et al., 2008). Based on the aforementioned assumptions, the desired sample size is 27.

**Small Effect Size**

Power analysis for a dependent sample *t*-test was conducted in G-POWER to determine a sufficient sample size using an alpha of 0.05, a power of 0.80, a small effect size (*dz* = 0.2), and one tail (Faul et al., 2008). Based on the aforementioned assumptions, the desired sample size is 156.

*References*

Faul, F., Erdfelder, E., Buchner, A., & Lang, A.-G. (2008). G*Power Version 3.1.2 [computer software]. Uiversität Kiel, Germany. Retrieved from http://www.psycho.uni-duesseldorf.de/abteilungen/aap/gpower3/download-and-register

Statistics Solutions. (2010). Sample Size Write-up [WWW Document]. Retrieved from http://www.statisticssolutions.com/resources/sample-size-calculator/dependent-samp…-test-1-tailed/