Chapter 9 – The Normal Distribution

Math 22

Introductory Statistics

Properties of the Normal Distribution

Basic properties of all normal distributions: The total area under the curve is equal to 1 The distribution is bell shaped and symmetric The curve extends to infinity in both directions The distribution is centered at the mean The mean is equal to the median

Properties of the Normal DistributionThe area under the curve between any

two points of the normal distribution is equal to the probability of observing a value between those two points.

z - ScoreNumber of standard deviations an

observation resides from the mean.

deviation standard

mean n observatio -z

x

xxz

The Standard Normal DistributionThe mean is equal to 0.The standard deviation is equal to 1.

Finding ProbabilitiesFinding probabilities using the TI – 83.Percentiles