1. Measures of Central Tendency

2. A numerical representation of the center of the most typical observations.
There are 3 measures of central tendency:
Mean, median, and mode

3. Mean
A.K.A “the average”
Found by adding all data and dividing by the total number of entries

4. Mean
A.K.A “the average”
Found by adding all data and dividing by the total number of entries
Ex. 50, 65, 75, 71,96, 65, 68, 61
Mean = 69

5. Median
The middle of the data when organized from least to greatest

6. Median The middle of the data when organized from least to greatest
Ex. 65, 75, 71,96, 50, 65, 68, 61
re-arrange:
50, 61, 65, 65, 68, 71, 75, 96

7. Median The middle of the data when organized from least to greatest
Ex. 65, 75, 71,96, 50, 65, 68, 61
re-arrange:
50, 61, 65, 65, 68, 71, 75, 96

8. Median The middle of the data when organized from least to greatest
Ex. 65, 75, 71,96, 50, 65, 68, 61
re-arrange:
50, 61, 65, 65, 68, 71, 75, 96
Find average if 2 #s in middle = 66.5

9. Mode The number that repeats the most often
Ex. 65, 75, 71,96, 50, 65, 68, 61

10. We got three different answers:
69 for mean, 66.5 for median, and 65 for mode
Which do you think best represents the data set?
65, 75, 71,96, 50, 65, 68, 61

11. OUTLIERS
Outliers are data that seem to be outside what appears to be “normal”
Outliers have the greatest influence on mean
50, 61, 65, 65, 68, 71, 75
Mean = 65

12. Create a set of data that has the following attributes:  N = 8 (items in the set of data)  Mean = 12  Median = 10  Mode = 9

13. Key Ideas
• The mode is the best measure of central tendency for data that represent frequency of choice such as favourite colour, clothing and shoe sizes, or most popular musical group.
• If all the numbers in a set of data are relatively close together, either the median or mean can be used as a measure of central tendency.
• If a data set contains unusually large or small numbers relative to the rest of the data, the median is usually the best measure of central tendency.