EWMA Forecast

The prediction of the process for time t, based on the exponentially weighted moving average at time t-1 to produce an exponential weighted moving average forecast. Used in the Wandering Mean EWMA Chart.

 for 2 < t < m+1

where:

xt-1 is the prior observation included in the analysis

the Starting value (value at time t=0) is either the Target value or process mean value (user defined)

λ is the value of the Weighting Factor (user defined). An optimal value of lambda can be determined that minimizes the Prediction Error

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).