Interquartile range

Definition

The interquartile range (IQR) measures the spread of the middle 50% of a dataset. It is calculated as the difference between the third quartile (Q3) and the first quartile (Q1).

5 Must Know Facts For Your Next Test

1. The IQR is used to describe the variability within a dataset.
2. It is not affected by outliers, making it a robust measure of spread.
3. To find Q1 and Q3, you need to split your data into four equal parts after sorting it.
4. IQR = Q3 - Q1.
5. A larger IQR indicates greater dispersion in the middle 50% of the data.

Review Questions

• How do you calculate the interquartile range (IQR)?
• Why is the IQR considered a robust measure of spread?
• What does a larger IQR indicate about a dataset?

Related terms

Quartile: Values that divide a dataset into four equal parts. The first quartile (Q1) marks the 25th percentile, and the third quartile (Q3) marks the 75th percentile.

Range:

The difference between the maximum and minimum values in a dataset.

Median:

$\text{The value separating}$ $\text{the higher half from}$ $\text{the lower half}$ $\text{of a data sample}$ $\text{or probability distribution}$. $\text{It corresponds}$ $\text{to Q2 or}\$ \text{the} \space \frac{50^{th}}{100} \space \text{percentile}$.