Finding Outliers with Fences

How do we calculate the IQR of a data set?

• Q1 + Q3

• Q3 - Q1

• Q1 - Q3

When using the IQR to find outliers, which formula will identify the upper fence?

• Q3 - 1.5(IQR)

• Q1 + 1.5(IQR)

• Q1 - 1.5(IQR)

• Q3 + 1.5(IQR)

When using the IQR to find outliers, which formula will identify the lower fence?

• Q3 - 1.5(IQR)

• Q1 + 1.5(IQR)

• Q1 - 1.5(IQR)

• Q3 + 1.5(IQR)

Given the data set: 23, 34, 27, 12, 30, 26, 28, 31, 34

Find the IQR.

• 8

• 9

• 24.5

• 32.5

DO NOT CLEAR YOUR CLACULATOR!

The IQR for the data set was 8 and Q1 = 24.5.

What is the lower "fence" for the data set?

• 24.5

• 8

• 12.5

• 1.5

Using the formula Q1 - 1.5(IQR), you get a lower fence of 12.5.

Data set: 23, 34, 27, 12, 30, 26, 28, 31, 34

Are there any values lower than 12.5 in the data set?

• yes

• no, there are no outliers on the low end of the data

Since there are numbers less than 12.5, what is the outlier?

• 12.5

• 12

DO NOT CLEAR YOUR CLACULATOR!

The IQR for the data set was 8 and Q3 = 32.5.

What is the upper "fence" for the data set?

• 44.5

• 8

• 12.5

• 1.5

Using the formula Q3 + 1.5(IQR), you get an upper fence of 44.5.

Data set: 23, 34, 27, 12, 30, 26, 28, 31, 34

Are there any values bigger than 44.5 in the data set?

• yes

• no

In our data set, what was the only outlier?

23, 34, 27, 12, 30, 26, 28, 31, 34

• 12

• 12.5

• 44.5