Microsoft Office Tutorials and References
In Depth Information
Deviating from the Middle
Skewed from the norm
There is deviation in a distribution, but who says the deviation has to be
uniform with deviation the same on both sides of the mean? Not all distributions
are normal — some are skewed, with more values clustered either below the
mean or above it:
When more values fall below the mean, the distribution is positively
skewed.
When more values fall above the mean, the distribution is negatively
skewed.
The following minitable has a few examples:
Values
Mean
Comment
1, 2, 3, 4, 5
3
No skew. An even number of values fall above
and below the mean.
1, 2, 3, 6, 8
4
The distribution is positively skewed. More
values fall below the mean.
1, 2, 8, 9, 10
6
The distribution is negatively skewed. More
values fall above the mean.
Figure 9-10 shows a distribution plot, where 1,000 values are in the
distribution, ranging between 1 and 100. The values are summarized in a table of
frequencies (discussed later in this chapter). The table of frequencies is the
source of the chart.
Figure 9-10:
Working
with skewed
data.
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