# st: inter and intra rater

 From Emma To statalist@hsphsun2.harvard.edu Subject st: inter and intra rater Date Mon, 22 Sep 2003 15:04:50 +0100

Dear Stata list users,

I wonder if someone could help me with the following, I am looking to calculate intra rater and inter rater correlations on the following data set. A continuous variable has been measured by 6 trainees on three different subjects (the three subjects have differing degrees of disease: small, moderate and large). All 6 trainees repeated the measurements on the three subjects on two separate occasions.

I have applied ICC as a measure for the agreement between the 6 raters; however STATA outputs 0* for the ICC whereas the data appears to show a reasonable agreement in measures between raters:

rater time1 time2
JT 22.5 22.5
KD 22.5 22.5
WD 22.5 22.5
NC 22 23
RP 22.5 22
ES 21.5 23

. loneway var1 rater

One-way Analysis of Variance for var1: measure2

Number of obs = 12
R-squared = 0.0870

Source SS df MS F Prob > F
-------------------------------------------------------------------------
Between rater .16666667 5 .03333333 0.11 0.9845
Within rater 1.75 6 .29166667
-------------------------------------------------------------------------
Total 1.9166667 11 .17424242

Intraclass Asy.
correlation S.E. [95% Conf. Interval]
------------------------------------------------
0.00000* 0.42817 0.00000 0.83921

Estimated SD of rater effect .
Estimated SD within rater .5400617
Est. reliability of a rater mean 0.00000*
(evaluated at n=2.00)

(*) Truncated at zero.

Also I wondered what measure I should use to consider the agreement between the repeat measures (should this be ICC also, and if so how should the data be set up, apologies to ask a basic question). Finally, is there anyway to consider the three subjects data together, i.e to combine the info for the small, moderate and large.

Kindest regards
Emma

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