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Outlier/Interquartile Range Calculator

Answer:

Interquartile range: 86.5
Outlier(s): 97, 152
Potential outlier(s): 879

See the outliers and potential outliers highlighted in the sorted data set here:
97, 152, 501, 571, 607, 614, 614, 615, 627, 638, 651, 665, 667, 684, 687, 692, 879


Solution:

The interquartile range, IQR, is the difference between Q3 and Q1. In this data set, Q3 is 675.5 and Q1 is 589. Subtract Q1, 589, from Q3, 675.5. $$ IQR = 675.5 - 589 = 86.5 $$ 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: $$ 589 - (1.5 \cdot 86.5) \text{ and } 675.5 + (1.5 \cdot 86.5) $$ $$ \text{Inner fences: } 459.25 \text{ and } 805.25$$

The outer fences are defined by: $$ Q1 - (3 \cdot IQR) \text{ and } Q3 + (3 \cdot IQR) $$ For this data set: $$ 589 - (3 \cdot 86.5) \text{ and } 675.5 + (3 \cdot 86.5) $$ $$ \text{Outer fences: } 329.5 \text{ and } 935 $$

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.

Outliers Outer fence Inner fence Inner fence Outer fence Outliers
329.5 459.25 805.25 935

If there are any outliers in this data set, they will either be less than 329.5 or greater than 935. Potential outliers will be between 329.5 and 459.25, inclusive or between 805.25 and 935, inclusive.

In this data set, the outlier(s) is/are: 97, 152
In this data set, the potential outlier(s) is/are: 879