# Within-subjects designs increase statistical power

## Each participant serves as their own control in within-subjects designs

**because participants serve as their own control.**

__Within-subjects designs increase statistical power.____necessitate more observations of the outcome to be able to effectively compare independent groups on an outcome.__

**Between-subjects designs**__further decrease statistical power in that many more observations of the outcome to detect significant effects. At least 20 -40 more observations of the outcome have to collected per variable entered into a simultaneous of hierarchial regression model in order to meet statistical power when trying to account for demographic, etiological, clinical, and confounding effects.__

**Multivariate analyses**Within-subjects designs, when coupled with with

__,__

**continuous outcomes**__,__

**large effect sizes**__and a__

**limited variance in the outcome**__, greatly increase statistical power.__

**large sample size**__are also easier to detect using within-subjects statistics because participants serve as their own control. Within-subjects design also provide more statistical power when__

**Small effect sizes**__are used.__

**small sample sizes**