How to Find Mean & Deviation

Mean deviation shows the amount of dispersion of a set of data.

The mean deviation shows how dispersed a set of values, or numbers, are. The mean is the average of the set of numbers. The mean deviation is the average distance each number is from the average of the set of numbers. For example, a set of numbers with a mean deviation of 5 means that, on average, each number in the set of numbers is 5 units higher or lower than the average. A higher deviation means a set of numbers is more dispersed. For example, a set of numbers with a mean deviation of 65 is more spread out than a set with a mean deviation of 1.

Instructions

1. Calculate the sum of a set of values. For example, if a basketball player scored 22, 14 and 18 points in three different basketball games, add 22 plus 14 plus 18, which equals 54.

2. Divide the sum by the number of games -- 54 divided by 3 equals 18. This is the mean.

3. Subtract the mean from each number in the set -- 22 minus 18 equals 4; 14 minus 18 equals -4; 18 minus 18 equals 0.

4. Determine the absolute value of each difference. Absolute value is the positive equivalent of a negative value. The absolute value of -4 is 4. The numbers 4 and 0 are already positive, so leave them positive.

5. Add the absolute values of the differences -- 4 plus 4 plus 0 equals 8.

6. Divide the result by the number of games -- 8 divided by 3 equals 2.67. The number 2.67 is the mean deviation of 22, 14 and 18. On average, the basketball player scored 2.67 points more or less than his average score for the three games.

References

• College of the Sequoias, Mathematics/Engineering Division: Mean Deviation
• Cliffs Notes: Measures of Central Tendency

Resources

• El Paso Community College: Describing Data: Numerical Measures