Glossary of statistical terms

facebook LinkedIn twitter Google+ Email

Kappa Statistic:

Kappa statistic is a generic term for several similar measures of agreement used with categorical data . Typically it is used in assessing the degree to which two or more raters, examining the same data, agree when it comes to assigning the data to categories. for example, kappa might be used to assess the extent to which (1) radiologist analysis of an x-ray, (2) computer analysis of the same x-ray, and (3) biopsy agree in labeling a growth "malignant" or "benign."

Suppose each object in a group of M objects is assigned to one of n categories. The categories are at nominal scale . For each object, such assignments are done by k raters.

The kappa measure of agreement is the ratio

K =   P(A) - P(E)

1 - P(E)
where P(A) is the proportion of times the k raters agree, and P(E) is the proportion of times the k raters are expected to agree by chance alone.

Complete agreement corresponds to K = 1 , and lack of agreement (i.e. purely random coincidences of rates) corresponds to K = 0 . A negative values of kappa would mean negative agreement - that is, the propensity of raters to avoid assignments made by other raters.

See also Cohen´s Kappa , Weighted Kappa

Browse Other Glossary Entries

Want to learn more about this topic? offers over 100 courses in statistics from introductory to advanced level. Most are 4 weeks long and take place online in series of weekly lessons and assignments, requiring about 15 hours/week. Participate at your convenience; there are no set times when you must to be online. Ask questions and exchange comments with the instructor and other students on a private discussion board throughout the course.

Survey Analysis

This course covers the analysis of data gathered in surveys.

Categorical Data Analysis

This course will cover the analysis of contingency table data (tabular data in which the cell entries represent counts of subjects or items falling into certain categories). Topics include tests for independence (comparing proportions as well as chi-square), exact methods, and treatment of ordered data. Both 2-way and 3-way tables are covered.

Back to Main Glossary

Promoting better understanding of statistics throughout the world

To celebrate the International Year of Statistics in 2013, we started a program to provide a statistical term every week, delivered directly to your inbox. The Word of the Week program proved to be quite popular, and continues. The Institute for Statistics Education offers an extensive glossary of statistical terms, available to all for reference and research. Make it your New Year's resolution to improve your own statistical knowledge! Sign up here. Rather not have more email? Simply bookmark our home page and check our “Stats Word of the Week” feature.

Want to be notified of future courses?

Student comments