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st: inter and intra rater

From   Emma <>
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.

Many thanks for any help you can provide.
Kindest regards

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