The third quartile (Q3) is the median of which portion?

• A. Median of lower half
• B. Mean of entire data
• C. Q2 - Q1
• D. Median of upper half

Answer: (D)

Quartiles divide data into four equal parts, and the third quartile marks the value that sits as the median of the upper half of the data when it’s ordered from smallest to largest. So, after lining up the data, you take the upper half and find its median. That value is Q3, representing the 75th percentile—about three quarters of the data fall at or below it.

For example, with eight ordered values 1, 2, 3, 4, 5, 6, 7, 8, the upper half is 5, 6, 7, 8. The median of that upper half is (6 + 7) / 2 = 6.5, so Q3 = 6.5.

The other options don’t describe Q3: the median of the lower half would be Q1, the overall median is Q2, and subtracting Q1 from Q2 isn’t a quartile.