The subjective approach compared subjectively determined
yield classes to management zones using areal
agreement and kappa statistics. Comparisons of management
zones from the SCMZ and YBMZ to subjective
yield classes are presented in Table 4. Across site
years, the YBMZ technique had the highest areal agreement
in two out of three site years. Areal agreement
ranged from 24 to 40% for the SCMZ technique and 32
to 59% for the YBMZ. Across site years, the SCMZ
technique had higher kappa statistics than the YBMZ
technique. Based on the guidelines provided in Table 2(Landis and Koch, 1977), the SCMZ technique had a
“slight” agreement with subjective yield classes for all
site years, whereas the YBMZ technique had “poor”
agreement in two out of three site years. Again, based
on these results, the SCMZ technique is relatively more
accurate than the YBMZ technique in differentiating
areas of low, medium, and high yields.