Measurement of Interobserver Disagreement: Correction of Cohen’s Kappa for Negative Values

Table 1

A 2 × 2 contingency table with marginal probabilities r and and with the entries in each cell as follows: first entry corresponds to , second entry corresponds to , and third entry is the weighted mean of the other two entries where .

Observer 1	Observer 2		Total
	Category 1	Category 2
Category 1	0
	Category 2			0
		Total					1.00