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From |
Robert Sutter <rdsutterjr@gmail.com> |

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

Subject |
st: Poisson Two Level Random Intercept ICC |

Date |
Fri, 1 Mar 2013 11:20:57 -0600 |

How is the intraclass correlation coefficient calculated when using a two level random intercept model? Below is the output from a two level model for the count of excess deaths (oediff2) as the dependent variable and the clusters are attending physicians. sigma_u is the random intercept variance. In Rabe-Hesketh’s book the ICC for binary data is derived by the following formula:random intercept variance/( random intercept variance + π2/3). π2/3 represents the variance of the logistic distribution. Can the same formula be used for count data by replacing π2/3 with the variance of oediff2? xtpoisson oediff2, i(attending_phy_id) normal Random-effects Poisson regression Number of obs = 75 Group variable: attending_ph~d Number of groups = 75 Random effects u_i ~ Gaussian Obs per group: min = 1 avg = 1.0 max = 1 Wald chi2(0) = . Log likelihood = -213.3618 Prob > chi2 = . ------------------------------------------------------------------------------ oediff2 | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- _cons | 2.617512 .0323429 80.93 0.000 2.554121 2.680903 -------------+---------------------------------------------------------------- /lnsig2u | -5.924562 4.653182 -1.27 0.203 -15.04463 3.195508 -------------+---------------------------------------------------------------- sigma_u | .0517009 .1202868 .0005409 4.94192 ------------------------------------------------------------------------------ Thanks, Bob * * 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/

**Follow-Ups**:**Re: st: Poisson Two Level Random Intercept ICC***From:*"JVerkuilen (Gmail)" <jvverkuilen@gmail.com>

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