Standard Normal Distribution

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. Move a point out into the tail. How far do you go when the probability stops changing? What happens when both points are on the negative side of the axis? Does the probability ever become a negative value?