Statistics
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
Z-Score ◦ Represents the number of standard deviations a given value falls from the mean. Z scores can be negative, positive, or zero
Highway driving. Mean speed is 56 mph Standard Deviation is 4 mph Find the z scores for 62, 47, & 56
Usual Score Unusual Score Very Unusual Score
Finding the z-score also gives you the percentile for a given value How to: Z
This means for z = 0, 50% of the population is below, 50% of the population is above. Z
Time in the shower (min.) Mean: 15 min. Standard Deviation: 8 min. Joe takes a shower for 25 minutes th Percentile 89% of people take a shower of 25 min. or shorter… 11% of people take a shower of 25 min. or longer