Sensitivity analysis
In this section, the performance of the VSSI, VSS, VSI, and FSSI
sampling schemes will be calculated and compared with the ANF, ANS, ANI,
and AATS measures for the U control chart by using various numerical
examples. The values of b, h, n, s, and f that used to calculate the
statistical criteria are based on the references in Section 2, which can
be referred for more information. The method used for calculating the
control limits (UCLi), the warning limits
(WLi), and the solution to determine the optimal values
of the measures and parameters of the control chart are based on
Shojaie-Navokh et al. [15]. In schemes that used two sample sizes
(n1, n2), the range for choosing values
equal;\(n_{1}=\left(1,\ldots,n_{0}\right)\ ,\ n_{2}=(n_{0},\ldots,50)\)and in schemes that used two sampling intervals (h1,
h2), the range for choosing values are\(h_{2}=\left(0.1,\ldots,h_{0}\right)\ ,\ h_{1}=(h_{0},\ldots,8)\).
Therefore, after determining the different levels for
u0, u+, λ, n0, and
h0, the results of calculating the statistical measures
for the sampling schemes are presented in Tables 1-12 (Tables 2-12 is
given in Appendix of this paper). Also, the values of obtained
parameters in each table for the VSSI, VSS, VSI, and FSSI sampling
schemes respectively are shown as follows: (n1,
n2, h1, h2,
WL1, WL2, UCL1,
UCL2), (n1, n2,
h0, WL1, WL2,
UCL1, UCL2), (n0,
h1, h2, WL, UCL), (n0,
h0, UCL).
Table 1 The results of
applying the VSSI sampling scheme when u+=3.2 and λ=0.04