Interpretation & Calculations
The smoothed standard deviation of the prediction errors.
is the Error Weighting Factor (user defined)
the one step ahead prediction error, et, is the calculated difference between the observation and the forecast
the starting value of λ is calculated (for m observations) as:.
Learn more about the SPC principles and tools for process improvement in Statistical Process Control Demystified (2011, McGraw-Hill) by Paul Keller, in his online SPC Concepts short course (only $39), or his online SPC certification course ($350) or online Green Belt certification course ($499).