.- help for ^icc23^ .- ^Calculation of ICC Models 2 and 3^ ^---------------------------------^ .^icc23^ , MOdel(#) LEvel(#) ^Description^ ^-----------^ ^icc23^ computes the intra-class correlation for random effects models based on repeated measures ANOVA. These models are ICC[2,1], ICC[2,k], ICC[3,1], and ICC[3,k], as described by Shrout and Fleiss, 1979 (see reference below). (For the ICC[1,1] and ICC[1,k] models based on a one-way ANOVA, see @loneway@). ^icc23^ runs a repeated measures ANOVA to derive the appropriate estimates and degrees of freedom. In the event there is a significant F-test for the ^classvar^ (e.g., a significant differernce among raters), the program will provide the p-value from the ANOVA table. Data must be in the "long" format. If not, use the @reshape@ command to reconfigure the data. Four types of ICC models are considered: ICC[2,1]: reflects the case where the same group of subjects is rated by k raters, interest is in the reliability of individual scores. In this model, raters are considered a representative sample of a population of similar raters. This model is a two-way random effects model. ICC[2,k]: is the same approach as ICC[2,1] above, but interest is in the reliability of the MEAN score, rather than among single observations. ICC[3,1]: reflects the case where the same group of subjects is rated by k raters, interest is in the reliability of individual scores. In this model, the only raters of interest are those participating in the study (e.g., there is no intention of generalizing the raters' scores to a larger population of raters). This model is considered a "mixed" model (subjects are random, raters are fixed). ICC[3,k]: is the same approach as ICC[3,1] above, but interest is in the reliability of the MEAN score, rather than among single observations. Three inputs are required: dv is the dependent variable classvar the class variable refers to factor that is repeated within subjects, e.g., raters, devices, time points, etc., e.g., the variable which would be entered as the repeated() variable in the ANOVA option. within_var refers to the "within subject" variable, e.g., subjects being assessed ^NOTE: The order of entry of the variables is critical!^ ^Options^ ^-------^ ^MO^del(#) refers to the type of model to be estimated. ICC model 2 is the default ( producing ICC[2,1] and ICC[2,k] estimates). ^LE^vel(#) the degree of precision of the confidence interval, entered as a decimal. The default is 95%, i.e., level(.95) Examples -------- For ICC[2,1] and ICC[2,k]: Two-way random effects (Subjects and raters are considered to be sampled from larger populations); 95% CIs are assumed. ^.icc23 score rater person_id^ For ICC[3,1] and ICC[3,k]: Two-way mixed model: Subjects are random, but raters are fixed (i.e., the raters are not considered a sample -- they are the only raters of interest); 90% CIs are requested. ^.icc23 score rater person_id, model(3) level(.90)^ References ---------- Shrout PE, FLeiss JL. Intraclass correlation: uses in assessing rater reliability. Psychol Bull, 1979; 86: 420-428. Portney LG, Watkins MP. Foundations of Clinical Research: Applications to Practice (2nd ed.). Prentice-Hall, Inc: Upper Saddle River, NJ., 2000. Author ------ Paul F. Visintainer, PhD Baystate Health System Springfield, MA 01089 visint46@gmail.com Luis C.Orozco, MD, MSc Facultad de Salud Universidad Industrial de Santander Colombia lcorovar@gmail.com Also see -------- Manual or on-line help for: @loneway@, @reshape@, @iclassr@, @iclassr2@