In Horn's Algorithm, IQR equals what?

In Horn's Algorithm, IQR equals what?

• A. Q1 - Q3
• B. Q3 + Q1
• C. Q3 - Q1
• D. Q1 + IQR

Answer: (C)

IQR measures the spread of the middle half of the data. It is defined as the difference between the third quartile and the first quartile, capturing how wide that central region is. So IQR equals Q3 minus Q1. This makes sense because you’re measuring a length, not a sum, and it reflects how far the central values are from each other. In practice, outlier-detection rules often use IQR to set fences like lower = Q1 − 1.5·IQR and upper = Q3 + 1.5·IQR, highlighting values outside that central band. The other options would either sum quantities or mix in IQR with Q1 in a way that doesn’t represent a width (for example, adding to Q1 can equal Q3, which is a percentile, not a dispersion measure).

IQR measures the spread of the middle half of the data. It is defined as the difference between the third quartile and the first quartile, capturing how wide that central region is. So IQR equals Q3 minus Q1. This makes sense because you’re measuring a length, not a sum, and it reflects how far the central values are from each other. In practice, outlier-detection rules often use IQR to set fences like lower = Q1 − 1.5·IQR and upper = Q3 + 1.5·IQR, highlighting values outside that central band. The other options would either sum quantities or mix in IQR with Q1 in a way that doesn’t represent a width (for example, adding to Q1 can equal Q3, which is a percentile, not a dispersion measure).