2.2.2. The Sensitivity of the DEM Parameters to the Stacking Angle

In order to explore the sensitivity of the external input DEM parameters on the stacking angle, a Plackett–Burman (PB) test with 11 factors and 1 central point was designed using the software Design-Expert version 12 (Stat-Ease, Inc., Minneapolis, MN, USA). There were 9 real variables (A to I), and 2 other virtual variables (J and K) were used to estimate the errors, while each parameter was set to low and high levels, according to the recommended range value. According to related studies [15–18] and a large number of pre-tests in the early stage, the ranged of each parameter were selected, as listed in Table 1.


**Table 1.** The parameter table of the Plackett–Burman test.
