Outlier

An Outlier is a data value that is not in the typical population of data, that is, extreme values. In a normal distribution, outliers are typically at least 3 standard deviations from the mean.

You specify a treatment by defining what constitutes an outlier (for example, all values in the top and bottom 5 percent of values) and how to replace outliers.

For example:

Mean of an attribute distribution=10

Standard deviation=5

Outliers are values that are:

• Less than -5 (The mean minus 3 times the standard deviation)

• Greater than 25 (The mean plus three times the standard deviation)

Then, in this case you can either replace the outlier -10 with Null or with 5.