1.5 times the H-spread.
Step
See also
Fence, H-SpreadExplore with Wolfram|Alpha
References
Tukey, J. W. Exploratory Data Analysis. Reading, MA: Addison-Wesley, p. 44, 1977.Referenced on Wolfram|Alpha
StepCite this as:
Weisstein, Eric W. "Step." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Step.html