“ I n God we trust, all others bring data.” Edwards Deming, American statistician and professor, is well known for this statement that has now become a motto for many scientists (Hastie et al., 2009, p. 4). And so we would also like to make an attempt to bring “data” into this chapter and talk about probability, causality, and chance. Before we do that there are two more quotes from Deming that we would like to share, “The most important things cannot be measured” (1991, p. 27). He thought that we couldn’t measure in advance things that are important, because sometimes at the time of measuring, we don’t understand that they are important. “The most important things are unknown or unknowable” (Deming, 1982, p. 121).