This worksheet allows you to explore the concept of probability as area under the standard normal distribution curve. Move the points z_a and z_b along the horizontal axis to compute the probability P(z_a < z < z_b).

Prove the Empirical Rule (the "68-95-99.7 Rule") to yourself.[br]Move a point out into the tail. How far do you go when the probability stops changing?[br]What happens when both points are on the negative side of the axis? Does the probability ever become a negative value?