Measures of Central Tendency Educational Assessment Unit Department for Curriculum Management

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

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.

Measures of Central Tendency Mean … the average score * is sensitive to extreme scores ex. 1 2 3 4 5 6 7 8 9 10 Mean = 5.5 (median = 5.5) ex. 1 2 3 4 5 6 7 8 9 20 Mean = 6.5 (median = 5.5) ex. 1 2 3 4 5 6 7 8 9 100 Mean = 14.5 (median = 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

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

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

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 = 34 - 1 = 33

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-

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?

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-