1. The Standard Normal Bell Curve
The Bell Curve
Normal Distribution – shows data that vary randomly from the mean.
Normal Curve – The pattern the data form is a bell-shaped curve.
The Standard Normal Bell Curve
68% of the data fall within one standard deviation of the mean
95% of the data fall within two standard deviations of the mean 1

2. Using the Standard Normal Curve
Ex 1) A survey of the employees of XYZ Corporation found that the mean of the morning commute times to work was 18 minutes. The standard deviation was 4 minutes. Sketch a normal curve showing the commute times at one, two, and three standard deviations from the mean.
What values are one standard deviation from the mean?
What percent of the data can you expect to find between 18 and 22 minutes?
Of 124 commuters, how many could you expect to be driving between 22 and 25 minutes to work? 2