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Outlier/Interquartile Range Calculator

Answer:

Interquartile range: 148
Outlier(s): none
Potential outlier(s): 99, 203

See the outliers and potential outliers highlighted in the sorted data set here:
99, 203, 509, 527, 528, 531, 542, 550, 572, 574, 649, 660, 664, 669, 676, 688, 691, 694, 892


Solution:

The interquartile range, IQR, is the difference between Q3 and Q1. In this data set, Q3 is 676 and Q1 is 528. Subtract Q1, 528, from Q3, 676. $$ IQR = 676 - 528 = 148 $$ You can use the 5 number summary calculator to learn steps on how to manually find Q1 and Q3.

To find outliers and potential outliers in the data set, we first need to calculate the value of the inner fences and outer fences. The inner fences are defined by: $$ Q1 - (1.5 \cdot IQR) \text{ and } Q3 + (1.5 \cdot IQR) $$ For this data set: $$ 528 - (1.5 \cdot 148) \text{ and } 676 + (1.5 \cdot 148) $$ $$ \text{Inner fences: } 306 \text{ and } 898$$

The outer fences are defined by: $$ Q1 - (3 \cdot IQR) \text{ and } Q3 + (3 \cdot IQR) $$ For this data set: $$ 528 - (3 \cdot 148) \text{ and } 676 + (3 \cdot 148) $$ $$ \text{Outer fences: } 84 \text{ and } 1120 $$

The inner and outer fences are listed below. Potential outliers are any values in our data set that fall between the inner fences and outer fences, inclusive. Outliers are any values that fall outside of the outer fences.

OutliersOuter fenceInner fenceInner fenceOuter fenceOutliers
843068981120

If there are any outliers in this data set, they will either be less than 84 or greater than 1120. Potential outliers will be between 84 and 306, inclusive or between 898 and 1120, inclusive.

In this data set, there are no outliers.
In this data set, the potential outlier(s) is/are: 99, 203

outlier calculator

How To Use the Outlier Calculator

The online outlier calculator applies the interquartile range to determine if there are any outliers or potential outliers in a data set.  Simply enter your data set as a comma separated list into the calculator.

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