Thank you Michael for your observations about Sesame Street. Although included in your first observation, I think it should be a point by itself - engage the learner by making learning fun. Some times there are things that multivariate regression analysis cannot measure like the joy on children's faces or the rapture that seems to transport some Sesame Street viewers to another place. We can't always measure some facets of the human condition that makes life worthwile and a pleasure to experience. We can't always measure what counts.