Third quartile

Definition

The third quartile (Q3) is the median of the upper half of a data set, representing the 75th percentile. It separates the highest 25% of data from the rest.

5 Must Know Facts For Your Next Test

1. The third quartile is also known as Q3 or the upper quartile.
2. It represents the value below which 75% of the data fall.
3. To find Q3, you can use a formula or arrange data in ascending order and locate it manually.
4. In a box plot, Q3 marks the end of the box on the right side (for horizontal plots) or top side (for vertical plots).
5. The interquartile range (IQR) is calculated as Q3 minus Q1, where Q1 is the first quartile.

Review Questions

• What percentage of data falls below the third quartile?
• How is Q3 used in calculating the interquartile range?
• In which graphical representation can you visually identify Q3?

Related terms

First Quartile (Q1): The first quartile (Q1) is the median of the lower half of a data set, representing the 25th percentile.

Median:

The median is the middle value in an ordered data set, separating it into two equal halves.

Interquartile Range (IQR): The interquartile range (IQR) measures statistical dispersion and is calculated as $$IQR = Q_3 - Q_1$$.