1. Statistics

2.  Percentiles ◦ Divides a data set into 100 equal parts  A score of 1700 on the SAT puts students in the 72 nd Percentile. ◦ 72% score 1700 or below ◦ 28% score 1700 or higher

3.  Z-Score ◦ Represents the number of standard deviations a given value falls from the mean. Z scores can be negative, positive, or zero

4.  Highway driving.  Mean speed is 56 mph  Standard Deviation is 4 mph  Find the z scores for 62, 47, & 56

5. -3-2 0123 Usual Score Unusual Score Very Unusual Score

6.  Finding the z-score also gives you the percentile for a given value  How to: Z0.000.010.020.030.04 0.0.500.504.508.512.516 0.1.539.543.547.551.555 0.2.579.583.591.594.598 0.3.617.621.625.629.633 0.4.655.659.662.666.670 00.130.41

7. This means for z = 0, 50% of the population is below, 50% of the population is above. Z0.000.010.020.030.04 0.0.500.504.508.512.516 0.1.539.543.547.551.555 0.2.579.583.591.594.598 0.3.617.621.625.629.633 0.4.655.659.662.666.670 00.130.41

8.  Time in the shower (min.)  Mean: 15 min.  Standard Deviation: 8 min.  Joe takes a shower for 25 minutes..894 89 th Percentile 89% of people take a shower of 25 min. or shorter… 11% of people take a shower of 25 min. or longer