Exercise: Meibography, answer 1

Question 1: ‘What is meant by ‘simple kappa = 0.78’? What does this tell us?

Kappa is a measure of agreement, here between two observations on the gestalt scale made by the same observer. Kappa allows for the agreement which we would expect to see by chance, even if the two sets of observations were unrelated. We calculate the proportion of cases where the two observations agree, and the proportion of cases where we would expect agreement if the two observations were unrelated. The difference between these is the amount by which the agreement exceeds chance. We then divide this by the maximum value it could have, one minus expected agreement, to get kappa, the proportion of the possible non-chance agreement which we observed.

Kappa = 0.78 is usually regarded as good agreement, being between 0.6 and 0.8.

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