Here 1−q is similar to the λ parameter in the case of the EWMA, and G0 is the historical mean or target value. Parameter α represents the influence of the newest point or sample. It slightly adjusts the kurtosis of the weighting function. If α = 1, then the GWMA becomes an EWMA and if α = 1 and q = 0, the chart acts as a Shewhart chart. If α > 1, the influence of the newest point is increased; it is decreased if α < 1 as compared to the EWMA. For information more on the influence of the parameters of the GWMA, see Ref. [21].
The control limits for the GWMA are the following: