outlier calculations

calculate IQR

IQR = Q3 - Q1

Q3

75th percentile

Q1

25th percentile

• 25% of the values the distribution lie at or below

how to calculate Q1

median of the median (left side)

how to calculate Q3

median of the median (right side)

calculate inner fences (potential outliers)

• Q1 - (1.5 x IQR)

• Q3 + (1.5 x IQR)

  • Assume “x” is the value we think might be an outlier

calculate outer fences (extreme outliers)

• Q1 - (3 x IQR)

• Q3 + (3 x IQR)

  • Assume “x” is the value we think might be an outlier

Q2

50th percentile

what is a potential outlier

• Inner fences

  • If “X” is less than: Q1 - (1.5 x IQR)

  • If “X” is greater than: Q3 + (1.5 x IQR)

what is an extreme outlier

• If “x” is less than: Q1 - (3 x IQR)

• If “x” is greater than: Q3 + (3 x IQR)