Stata 15 help for icc

[R] icc -- Intraclass correlation coefficients

Syntax

Calculate intraclass correlations for one-way random-effects model

icc depvar target [if] [in] [, oneway_options]

Calculate intraclass correlations for two-way random-effects model

icc depvar target rater [if] [in] [, twoway_re_options]

Calculate intraclass correlations for two-way mixed-effects model

icc depvar target rater [if] [in], mixed [twoway_me_options]

oneway_options Description ------------------------------------------------------------------------- Main absolute estimate absolute agreement; the default testvalue(#) test whether intraclass correlations equal #; default is testvalue(0)

Reporting level(#) set confidence level; default is level(95) format(%fmt) display format for statistics and confidence intervals; default is format(%9.0g) -------------------------------------------------------------------------

twoway_re_options Description ------------------------------------------------------------------------- Main absolute estimate absolute agreement; the default consistency estimate consistency of agreement testvalue(#) test whether intraclass correlations equal #; default is testvalue(0)

Reporting level(#) set confidence level; default is level(95) format(%fmt) display format for statistics and confidence intervals; default is format(%9.0g) -------------------------------------------------------------------------

twoway_me_options Description ------------------------------------------------------------------------- Main * mixed estimate intraclass correlations for a mixed-effects model consistency estimate consistency of agreement; the default absolute estimate absolute agreement testvalue(#) test whether intraclass correlations equal #; default is testvalue(0)

Reporting level(#) set confidence level; default is level(95) format(%fmt) display format for statistics and confidence intervals; default is format(%9.0g) ------------------------------------------------------------------------- * mixed is required.

bootstrap, by, jackknife, and statsby are allowed; see prefix.

Menu

Statistics > Summaries, tables, and tests > Summary and descriptive statistics > Intraclass correlations

Description

icc estimates intraclass correlations for one-way random-effects models, two-way random-effects models, or two-way mixed-effects models for both individual and average measurements. Intraclass correlations measuring consistency of agreement or absolute agreement of the measurements may be estimated.

Options for one-way RE model

+------+ ----+ Main +-------------------------------------------------------------

absolute specifies that intraclass correlations measuring absolute agreement of the measurements be estimated. This is the default for random-effects models.

testvalue(#) tests whether intraclass correlations equal #. The default is testvalue(0).

+-----------+ ----+ Reporting +--------------------------------------------------------

level(#) specifies the confidence level, as a percentage, for confidence intervals. The default is level(95) or as set by set level.

format(%fmt) specifies how the intraclass correlation estimates and confidence intervals are to be formatted. The default is format(%9.0g).

Options for two-way RE and ME models

+------+ ----+ Main +-------------------------------------------------------------

mixed is required to calculate two-way mixed-effects models. mixed specifies that intraclass correlations for a mixed-effects model be estimated.

absolute specifies that intraclass correlations measuring absolute agreement of the measurements be estimated. This is the default for random-effects models. Only one of absolute or consistency may be specified.

consistency specifies that intraclass correlations measuring consistency of agreement of the measurements be estimated. This is the default for mixed-effects models. Only one of absolute or consistency may be specified.

testvalue(#) tests whether intraclass correlations equal #. The default is testvalue(0).

+-----------+ ----+ Reporting +--------------------------------------------------------

level(#) specifies the confidence level, as a percentage, for confidence intervals. The default is level(95) or as set by set level.

format(%fmt) specifies how the intraclass correlation estimates and confidence intervals are to be formatted. The default is format(%9.0g).

Examples

Setup . webuse judges

Calculate ICCs for one-way random-effects model . icc rating target

Same as above but test whether ICCs equal 0.5 . icc rating target, testvalue(.5)

Calculate ICCs for two-way random-effects model . icc rating target judge

Same as above but estimate consistency of agreement . icc rating target judge, consistency

Calculate ICCs for two-way mixed-effects model . icc rating target judge, mixed

Same as above but estimate absolute agreement . icc rating target judge, mixed absolute

Stored results

icc stores the following in r():

Scalars r(N_target) number of targets r(N_rater) number of raters r(icc_i) intraclass correlation for individual measurements r(icc_i_F) F test statistic for individual ICC r(icc_i_df1) numerator degrees of freedom for r(icc_i_F) r(icc_i_df2) denominator degrees of freedom for r(icc_i_F) r(icc_i_p) p-value for F test of individual ICC r(icc_i_lb) lower endpoint for confidence intervals of individual ICC r(icc_i_ub) upper endpoint for confidence intervals of individual ICC r(icc_avg) intraclass correlation for average measurements r(icc_avg_F) F test statistic for average ICC r(icc_avg_df1) numerator degrees of freedom for r(icc_avg_F) r(icc_avg_df2) denominator degrees of freedom for r(icc_avg_F) r(icc_avg_p) p-value for F test of average ICC r(icc_avg_lb) lower endpoint for confidence intervals of average ICC r(icc_avg_ub) upper endpoint for confidence intervals of average ICC r(testvalue) null hypothesis value r(level) confidence level

Macros r(model) analysis-of-variance model r(depvar) name of dependent variable r(target) target variable r(rater) rater variable r(type) type of ICC estimated (absolute or consistency)


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