IB Math Studies
Warm-Up Outliers - Day 20
Name: _______________________________ page 1
Date: ____________ Block: __________
Outliers are extraordinary data that are usually separated from the main body of the data. Outliers are either much larger
or much smaller than most of the data. There are several tests that identify data that are outliers.
A commonly used test involves the calculation of “boundaries”:

The UPPER BOUNDARY = upper Quartile (Q3) + 1.5 • IQR
Any data larger than the upper boundary is an outlier.

The LOWER BOUNDARY = lower quartile (Q1) – 1.5 • IQR
Any data smaller than the lower boundary is an outlier.
*Outliers are generally marked with an asterisk on a boxplot and it is possible to have more than one outlier at either end.
The whiskers extend to the last value that is not an outlier.
1.
Draw a boxplot for the following data, testing for outliers and marking them, if they exist, with an asterisk
on the boxplot.
3, 7, 8, 8, 5, 9, 10, 12, 14, 7, 1, 3, 8, 16, 8, 6, 9, 10, 13, 7
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Consider the following data set: 4, 5, 6, 6, 6, 7, 8, 9, 10
a)
Calculate the mean, median, and mode of this data.
Mean: _________
Median: ________
Mode: _________
b)
Now introduce an extreme value, 100, to the data. The data set is now 4, 5, 6, 6, 6, 7, 8, 9, 10, 100.
Recalculate the mean, median, and mode for this new data set.
Mean: _________
Median: ________
Mode: _________
c)
Comment on the affect that this extreme value had on the mean, median, and the mode. Which value is
most affected by the inclusion of an outlier?