In Horn's Algorithm, what is the upper fence value?

In Horn's Algorithm, what is the upper fence value?

• A. Q1 - 1.5 × IQR
• B. Q3 + 1.5 × IQR
• C. Q3 - 1.5 × IQR
• D. Q1 + 1.5 × IQR

Answer: (B)

Outlier thresholds in this approach come from the quartiles and the spread of the middle 50%. The interquartile range (IQR) is the difference between the third quartile (Q3) and the first quartile (Q1). To set a boundary on the high end, you take the upper quartile and add a multiple of the IQR. The conventional multiplier is 1.5, which creates a boundary that flags unusually large values without labeling normal variation as outliers. So the upper fence value is Q3 plus 1.5 times the IQR. For example, if Q3 is 20 and IQR is 10, the upper fence would be 20 + 1.5×10 = 35; values above 35 would be considered potential outliers.

Outlier thresholds in this approach come from the quartiles and the spread of the middle 50%. The interquartile range (IQR) is the difference between the third quartile (Q3) and the first quartile (Q1). To set a boundary on the high end, you take the upper quartile and add a multiple of the IQR. The conventional multiplier is 1.5, which creates a boundary that flags unusually large values without labeling normal variation as outliers. So the upper fence value is Q3 plus 1.5 times the IQR. For example, if Q3 is 20 and IQR is 10, the upper fence would be 20 + 1.5×10 = 35; values above 35 would be considered potential outliers.