1. Unit Three
Central Tendency

2. What is Central Tendency?
Central Tendency is a way to analyze numbers so that we can get more meaning from them.
For example, if you made a 65% on a test, you would be disappointed. When you find out the class average is a 43%, you would feel pretty smart!

3. Data Set
A collection of numbers being analyzed for central tendency is called a data set.

4. Mean
The average.
Add all numbers together, then divide by the total number of values.

5. Median
The number that falls in the exact middle when numbers are placed in order (least to greatest). If there is an even amount of numbers, find the mean of the two numbers closest to center.

6. Mode The number that appears MOST often in the data set.
The mode is 6 hours per week.

7. Range
The difference between the largest and the smallest numbers in the data set.
Data Set: 56, 23, 12, 78, 10
The range is 68.
78 (the largest #) (the smallest #) = 68

8. Lower Extreme
The smallest number in the data set.

9. Quartiles The median for the bottom half of the data.
Lower (First)
Upper (Third)
The median for the bottom half of the data.
The median for the upper half of the data.

10. Interquartile Range
Interquartile Range is the difference between the Upper (Third) Quartile and the Lower (First) Quartile.

11. Upper Extreme The greatest number in the data set.
-4, -2, 1, 0, 3, 4, 8, 9

12. Outlier
A value that "lies outside" (is much smaller or larger than) most of the other values in a set of data.
For example in the scores 3,25,27,28,29,32,33,85, both 3 and 85 are "outliers".

13. Box-and-Whisker Plots
5 Number Summary information is depicted on a box-and-whisker plot/graph.

14. 5 Number Summary
A 5 Number Summary shows five numbers related to the data set: The lower extreme, the first quartile, the median, the third quartile, and the upper extreme.