The Correlation Coefficient and Coefficient of Determination (Old, fast version)
I have an updated and revised (slower and otherwise improved) version of this video available at: • Video
A look at the Pearson correlation coefficient (r), the coefficient of determination (r^2), some of their properties and a few examples.
One of the data sets used is estimated from a figure given in:
Singer et al. (2004). Empathy for pain involves the affective but not sensory components of pain. Science, 303:1157--1162.