Empirical Rule and z-score Probability

Empirical Rule The Empirical Rule applies to a normal, bell-shaped curve than is symmetrical about the mean. It states that within one standard deviation of the mean (both left-side and right-side) there is about 68% of the data; within two standard deviations of the mean (both left-side and right-side) there is about 95% of the data; […]

The Impact of Innumeracy

By the time we reach voting age, almost all Americans have at least a high school education. That means we have been exposed to numerous math courses, and hopefully passed them. But that does not mean we have a good sense of numbers. Innumeracy in the modern sense means that one does not have a […]

When do I substract from 1?

Always sketch the normal curve situation first. Remember the Standard Normal Distribution tables almost always give the area/probability from left infinity to the z-value in question; check for sketches on the tables you use to confirm. The Excel Norm.xxx functions also return the probability to the left of the z-value in question. If the problem […]