Touchstone2 offers a direct-manipulation interface for generating and examining trade-offs in experiment designs. Based on interviews with experienced researchers, we developed an interactive environment for manipulating experiment design parameters, revealing patterns in trial tables, and estimating and comparing statistical power. We also developed TSL, a declarative language that precisely represents experiment designs. In two studies, experienced HCI researchers successfully used Touchstone2 to evaluate design trade-offs and calculate how many participants are required for particular effect sizes. We discuss Touchstone2’s benefits and limitations, as well as directions for future research.