This document defines and provides the formula for calculating mean deviation, which is a measure of variation that uses all the scores in a distribution. It is more reliable than range. Mean deviation is calculated by finding the absolute difference between each score and the mean, summing the absolute differences, and dividing by the number of observations. Two examples of calculating mean deviation for sets of data are provided, along with exercises asking students to find the mean deviation of additional data sets and define standard deviation.

8. MATH

9. WELCOMEMATH

10. MA
TH
MEAN
DEVIATION
(for ungrouped data)

11. MA
TH
Definition:
The MEAN DEVIATION, or
average deviation, is the
dispersion of the data
about the mean of these
data.

12. MA
TH
Definition:
The MEAN DEVIATION is a
measure of variation that
makes use of all the
scores of the distribution.

13. MA
TH
The MEAN DEVIATION is
more reliable than the
RANGE.

14. MA
TH
Formula
M.D. = ∑|x – x|
n
(for ungrouped data)
where x is the scores of the
distribution
x is the meann is the number of
observations

15. Steps
1. Find the mean of the
scores.
2. Find the absolute difference
between each score and the
mean.
3. Get the sum of the absolute
differences.
4. Divide it by n.

16. Ex. 1
Find the mean deviation of
the given set of data.
85 96 76 108
85 80 85 100
70 95

17. Ex. 2
Find the mean deviation of
the given set of data.
3 13 11 11
5 4 2

18. You
Can
Do It!
Work-In-Pair 
Two Heads Are Better Than One
Find the mean deviation.
1. Science achievement test
scores: 60, 75, 80, 85, 90, 95
2. Height (in cm) of five grade 7
students: 150, 154, 148, 156,
150

19. HOME
WORK
Learning is fun! 
Answer the following.
1. Define STANDARD
DEVIATION.
2. What are the steps in
computing the standard
deviation for ungrouped data?