Applies to: @RISK 4.x and Up

 

What is the shift factor of a distribution, and why is it used?

 

The shift factor, accessed via RiskShift(), moves a distribution along the x-axis: positive shifts move it right, negative shifts move it left. It effectively adds (or subtracts) a constant to all points in the distribution.

Use cases:

• Defining distributions: You can add a shift factor to move distributions without changing their shape, e.g., RiskLognorm(10,10,RiskShift(3.7)) shifts it 3.7 units right. Display it via the Define Distributions dialog or always show it in Utilities » Application Settings » Distribution Entry. Avoid using it for distributions with built-in location parameters, like the normal distribution.

• Fitted distributions: Shift factors allow fitting a distribution shape to data that otherwise violate parameter limits. For instance, a 2-parameter log-normal cannot be negative, but if your data are log-normal-shaped with some negative values, a negative shift factor effectively creates a 3-parameter log-normal to match your data.

 

Related Article:

Truncate and Shift in the Same Distribution