rESEARCH

1. Measure of
Variability
Research 9
Special Science Class

2. Measure of Variability
•It is used to determine the spread
of scores in a distribution. It gives
an idea of how much the scores
deviate from the center of the
distribution.
•There are several measures of
variability: range, mean deviation,
variance, and standard deviation.

3. Measures of Variability
There are several measures of variability:
Range
Mean Deviation
Variance
Standard Deviation

4. Range
•It is the full distance between the
lowest and highest scores in a
distribution.
•It is the easiest and the quickest to
compute.

5. Range
•It can be classified into:
a. Exclusive Range – the
difference between the highest
score (HS) and the lowest score
(LS) in the distribution, (HS – LS).
b. Inclusive range – the difference
between the highest score and
lowest score plus one, (HS - LS +
1)

6. Mean Deviation
•The mean deviation gives a rough
estimate of the distances of the
individual scores from the mean of
the scores. It is the average of the
absolute deviations of the scores
from the mean.

7. Mean Deviation
•The mean deviation gives a rough
estimate of the distances of the
individual scores from the mean of
the scores. It is the average of the
absolute deviations of the scores from
the mean.

8. Mean Deviation
•In mathematical form it is:

9. Mean Deviation
•Steps in Getting the Mean Deviation:
1. Get the mean score.
2. Subtract the mean from each value.
3. Take the absolute value of each
result.
4. Add them up.
5. Divide this value by the total number
of observations or score.

10. Variance
•Squaring deviations of scores from
the mean gives positive squared
deviations. You call this variability the
variance of the set of scores.
•You can numerically describe the
consistency (precision) of
measurement using variance.
•This measures how far or close the
measurements are from the mean
(average.)

11. Variance
•It is defined as the average of the
squared difference of the
measurement (𝑥) from the mean
(𝑋). The formula to find variance
is:
𝝈𝟐
=
(𝑥−𝑋)2
𝑁

12. Variance
•Below are the steps in finding the
variance of a set of scores:
1. Find the mean of the scores.
2. Get the deviation of each score from
the mean.
3. Square each deviation from the
mean.
4. Get the sum of the squared
deviations from the mean.

13. Variance
•Continuation…
5. Divide this sum by the total number
of scores. The quotient is the
variance of the set of scores.Get the
deviation of each score from the
mean.

14. Variance
•𝝈𝟐 =
(𝑥−𝑋)2
𝑁
• Where N is the number of
measurements done.