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i
thus represents the number of sample units with reference class label
j
that have
been labeled as class
i
by the classifier. The following accuracy measures are also
reported with the option
-cm|--confusion
:
•
User's accuracy (UA) per class: proportion of sample units predicted as this class
that are correct (related to the commission error as 1
−
UA);
•
Producer's accuracy (PA) per class: proportion of sample units referenced as this
class that are correct (related to the omission error as 1
−
PA) ;
•
Overall accuracy (OA): proportion of all sample units that were predicted correctly;
•
Kappa Coefficient: proportion of agreement after chance agreement is removed
from consideration (Cohen 1960).
The confidence limits for the estimated accuracy are reported in brackets after each
measure, according to a 95% confidence level. Note that this is only an approximated
limit, where the measure is considered as Gaussian distributed. This approximation
is valid in case of a simple random sampling design (uniform distribution). For other
(e.g. stratified) designs, different formulae must be applied (Wolter 1984; Stehman
1996).
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