Outlier/Interquartile Range Calculator
Answer:
Interquartile range: 140
Outlier(s):
55
Potential outlier(s):
132
See the outliers and potential outliers highlighted in the sorted data set here:
55, 132, 508, 509, 513, 524, 535, 537, 568, 578, 579, 608, 625, 646, 654, 663, 664, 670, 686, 801
Solution:
The interquartile range, IQR, is the difference between Q3 and Q1. In this data set, Q3 is 658.5 and Q1 is 518.5. Subtract Q1, 518.5, from Q3, 658.5. $$ IQR = 658.5 - 518.5 = 140 $$ 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: $$ 518.5 - (1.5 \cdot 140) \text{ and } 658.5 + (1.5 \cdot 140) $$ $$ \text{Inner fences: } 308.5 \text{ and } 868.5$$
The outer fences are defined by: $$ Q1 - (3 \cdot IQR) \text{ and } Q3 + (3 \cdot IQR) $$ For this data set: $$ 518.5 - (3 \cdot 140) \text{ and } 658.5 + (3 \cdot 140) $$ $$ \text{Outer fences: } 98.5 \text{ and } 1078.5 $$
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 |
| 98.5 | 308.5 | 868.5 | 1078.5 |
If there are any outliers in this data set, they will either be less than 98.5 or greater than 1078.5. Potential outliers will be between 98.5 and 308.5, inclusive or between 868.5 and 1078.5, inclusive.
In this data set, the outlier(s) is/are:
55
In this data set, the potential outlier(s) is/are:
132