FRAME 43.
SUMMARY OF THE MEASURES OF DISPERSION
RANGE
The range is the difference between the highest and lowest values in a group of observations.
The range is simple to compute but only considers the two extreme values. The range should be
used only in cases where a quick, cursory look at the data is required.
STANDARD DEVIATION
The standard deviation is a unit of measure of dispersion. The more variability or scatter in a
group of data, the larger the standard deviation will be. Standard deviation is computed as
shown.
Population Standard Deviation = σ =
Σ(X - u) 2
N
Σ(X-X) 2
Sample Standard Deviation = s =
n-1
Note that In the denominator, we are using n-1 rather than n. This expression, n-1, allows for
degrees of freedom (df). Df will not be discussed here because it is beyond the scope of this
subcourse. It is treated in inferential rather than descriptive statistics.
Proceed to the Practice Exercise for Lesson 2.
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