Baker, Shelton, Baibazarova, Hay, and van Goozen (2013) studied the extent to which skin conductance activity (SCA) in toddlers could predict aggression in the toddlers two years later. In their study, they reported that the correlation between SCA and aggressive antisocial behavior at a baseline stage was r = −.34, p = .005. Given that only one predictor variable was tested, what must the value of the standardized beta coefficient (β) be equal to for this result?