Echoing these recommendations, articles describe how to simulate the SDM using a wide variety of physical objects, a graphing calculator, or a computer. The demonstrations tend to use skewed or bimodal populations, so that students are impressed with the counter-intuitive result. Invariably, the authors anticipate that “the student will observe that the center of the distribution remains about the same and the distribution becomes narrower. That is, as sample size gets larger the approximations to the mean do not get better, but the variability about the mean decreases.” (Koehler 2006, pp. 264-265).