1. Measures of Central Tendency
Educational Assessment Unit Department for Curriculum Management

2. Measures of Central Tendency
Mean … the average score
Median … the value that lies in the middle after ranking all the scores
Mode … the most frequently occurring score

3. Measures of Central Tendency
Which measure of Central Tendency should be used?
The measure you choose should give you a good indication of the typical score in the sample or population.

4. Measures of Central Tendency
Mean … the average score * is sensitive to extreme scores ex
Mean = 5.5 (median = 5.5) ex
Mean = 6.5 (median = 5.5) ex
Mean = 14.5 (median = 5.5)

5. Measures of Central Tendency
Median
… is not sensitive to extreme scores
… use it when you are unable to use the mean because of extreme scores

6. Measures of Central Tendency
Mode
… does not involve any calculation or ordering of data
… use it when you have categories (e.g. occupation)

7. Variation or Spread of Distributions
Range
It compares the minimum score with the maximum score
Max score – Min score = Range
It is a crude indication of the spread of the scores because it does not tell us much about the shape of the distribution and how much the scores vary from the mean
Two distributions may have the same range but in one distribution the scores may be tightly packed around the mean while in the other they may be more spread out from the mean.
Educational Assessment Unit Department for Curriculum Management

8. Variation or Spread Measures that indicate the spread of scores:
Range - the difference between the
highest and lowest scores
Ex. 2, 5, 9, 17, 8, 27, 1, 34
Range = = 33

9. Example
Find the mean, median, mode, and range from the following set of data values:
2, 4, 9, 13, 16, 22
Mean-
Median-
Mode-
Range-

10. Example 2
Find the mean, median, mode, and range from the following set of data values:
60, 64, 69, 73, 76, 122
Mean-
Median-
Mode-
Range-
* What does the value of 122 do to the data set?

11. How would the values change without 122?
Find the mean, median, mode, and range from the following set of data values:
60, 64, 69, 73, 76
Mean-
Median-
Mode-
Range-