What does Q3 represent in a five-number summary?

In a five-number summary, Q3, or the third quartile, specifically represents the median of the upper half of the data. To understand this, consider how a five-number summary is structured, which typically consists of the minimum value, Q1 (the first quartile), the median (Q2), Q3, and the maximum value.

Q3 effectively divides the top 50% of the data into two equal parts, highlighting the value below which 75% of the data points fall. This positioning makes it a crucial component for understanding the distribution and spread of data, particularly in identifying outliers or assessing skewness.

The overall average of the dataset and the minimum value do not convey the same information as Q3, and the median of the lower half refers to Q2, not Q3. Thus, defining Q3 as the median of the upper half accurately describes its function within the five-number summary.