help kappaetc, ttest (SJ18-4: st0544)

Title

kappaetc, ttest -- Paired t tests of agreement coefficients

Syntax

kappaetc
name1 == name2
[, ttest options]

where name1 and name2 are results previously stored by
kappaetc as

kappaetc
varlist
[if] [in]
[weight], store(name1)
[kappaetc_options]

kappaetc
varlist
[if] [in]
[weight], store(name2)
[kappaetc_options]

ttest perform paired t tests of agreement coefficients

level(#) set confidence level; default is
level()

noheader suppress output header

notable suppress coefficient table

replay replay results in name1 and name2

format_options control column formats

Description

kappaetc with the ttest option performs paired t tests of the
differences between correlated agreement coefficients. It implements the
linearization method discussed in Gwet (2016).

The two sets of agreement coefficients are assumed to be based on the same
subjects rated by different groups of raters or rated repeatedly by the same
group of raters. The test statistics are based on differences of the
subject-level agreement coefficients.

Options

ttest performs paired t tests of correlated agreement coefficients.

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

noheader suppresses the report about the number of subjects. Only the
coefficient table is displayed.

notable suppresses the display of the coefficient table.

replay replays the two sets of agreement coefficients to be tested.

format_options are the same as with
kappaetc.

Example

The example data are drawn from [R] kappa.

Test the difference of agreement among the first three and last two
raters:

. webuse p615b

. kappaetc rater1-rater3, store(group1)

. kappaetc rater4 rater5, store(group2)

. kappaetc group1==group2

Stored results

kappaetc with the ttest option stores the following in r():

Scalars

r(N) number of subjects

r(level) confidence level

Macros

r(cmd) kappaetc

r(cmd2) ttest

r(results1) name1 of the first stored results

r(results2) name2 of the second stored results

Matrices

r(b) coefficient vector

r(table) information from the coefficient table

r(se) standard errors of differences

r(df) difference-specific degrees of freedom

r(estimable) whether difference could be estimated

Reference

Gwet, K. L. 2016. Testing the difference of correlated agreement coefficients
for statistical significance. Educational and Psychological Measurement
76: 609-637.

Author

Daniel Klein

International Centre for Higher Education Research Kassel

Kassel, Germany

klein@incher.uni-kassel.de

Also see

Article: Stata Journal, volume 18, number 4: st0544

Help: [R] ttest, [R] kappa, [R] icc,
kappaetc (if installed)