1. Measures of Central Tendency

2. Measures of Central Tendency
Measures of central tendency include mean, median, and mode. They describe the “center” of a set of data.

3. Measures of Variability
Measures of variability such as range, interquartile range, and mean absolute deviation. It is the average distance between each data value and the mean or median, so it shows the variation of the data from the mean.

4. What is the mean and how do we find it?
The mean is useful for predicting future results when there are no extreme values in the data set.  However, the impact of extreme values on the mean may be important and should be considered.

5. Find the mean for the following data
13, 18, 13, 14, 13, 16, 14, 21, 13 ( )= ÷ 9 = 15 Note: that the mean isn't a value from the original list. This is a common result. You should not assume that your mean will be one of your original numbers.

6. Find the mean
 8, 9, 10, 10, 10, 11, 11, 11, 12, 13

9. What is the median and how do we find it?
The median may be more useful than the mean when there are extreme values in the data set as it is not affected by the extreme values.

10. Find the median for this set of data
13, 15, 26, 16, 12, 19, 23, 24 Step 1: Put list in numerical order 12, 13, 15, 16, 19, 23, 24, 26 Step 2: count down from opposite sides to locate the middle number. If the data set is even you will need to find the average of the two middle numbers = ÷ 2 = 17.5

11. Find the median
24, 31, 15, 16, 11, 26, 29

14. What is mode and how do we find it?
The mode is useful when the most common item, characteristic or value of a data set is required.

15. Find the mode for the following data
Step 1: cross off single numbers. Step 2: count the number of times each of the remaining numbers occur.

16. Find the mode
75, 45, 63, 62, 63, 75, 92, 102

17. Find the mode
23, 15, 89, 75, 14, 63, 57