Probability Theory

The Normal Probability Density Function (cont.):

• The table gives Pr {Z < a} where the first digit of a is on the left-hand-side column and the last digit is on the top row. For example:

• They show the procedure of using the equivalence of events to transform normal probability calculations to a form where answers can be looked up using the table.
• In situations where Excel spread sheets can be accessed, similar results can be derived using built-in functions. For example, “=NORMDIST (5, 9, 2, TRUE)” gives the value 0.02275, where the TRUE refers to the cumulative probability that X is less than a. A false would give the probability density function value at the point X = a.