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From |
Red Owl <rh.redowl@liu.edu> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
st: Re: Kappa PABAK |

Date |
Wed, 31 Jul 2013 22:13:21 +0000 |

I am not aware of a user-written Stata program for calculating PABAK, but it is a straightforward calculation. For a discussion of PABAK (and some cautions and alternatives) see: Cunningham, M. (2009). More than just the kappa coefficient: A program to fully characterize inter-rate reliability between two raters. Paper 242-2009. SAS Global Forum 2009. Retrieved from http://support.sas.com/resources/papers/proceedings09/242-2009.pdf In a 2 x 2 table, the proportion of observed agreement is calculated as: p(observed) = (a + d) / N. and, then: PABAK = 2 * p(observed) - 1 For polytomous ratings, you could also consider linear or quadratically weighted kappa, as provided in -kap- and -kapwgt- in Stata and then report the prevalence and bias indices shown below along with kappas. In the 2 x 2 case, you can use the following simple formulas from p. 2 in Cunningham(2009) to calculate prevalence and bias indices. (These formulas can easily be extended.) Prevalence Index = (a-d)/N Bias Index = (b-c)/N Below is a simple toy example in Stata for a 2 x 2 case: * Build rater x rater data matrix from Figure 2, Cunningham (2009). matrix input A = (95, 4 \ 1, 0) * Calculate and display PABAK plus prevalence and bias indices. scalar pabak = 2 * (A[1,1]+A[2,2])/(A[1,1]+A[1,2]+A[2,1]+A[2,2])-1 scalar prevndx = (A[1,1]-A[2,2])/(A[1,1]+A[1,2]+A[2,1]+A[2,2]) scalar biasndx = (A[1,2]-A[2,1])/(A[1,1]+A[1,2]+A[2,1]+A[2,2]) di %5.4f "PABAK = " pabak di %5.4f "Prevalence Index = " prevndx di %5.4f "Bias Index = " biasndx Red Owl redowl@liu.edu >> Is there a user command for prevalence adjusted bias adjusted kappa >> (PABAK)? I have searched the statalist and can't seem to find one. >> >> Thank you, >> >> Jordan * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

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