Intra rater reliablity and icc

[izzy turner]

Hi, I have been struggling to find the best solution to measure intra rater reliability, and hope someone can help. I'm aware of the ICC function and have seen some posts on that, but this seems to relate to inter-rater reliability only. I am measuring the same x-ray angle three times(1-3) at five timepoints (t1-t5) and would like to see if the measurements are reliable. There's quite a bit of missing data, I have about 50 observations (nncode). The data is currently in the format below, although I'm aware I may need to change this to long and am happy to do that. Any assistance gratefully received.

nncode	t1_1	t1_2	t1_3	t2_1	t2_2	t2_3
1	1.80	1.5	4.7	8.4	7.2	6.6
2	4.80	5.8	5.8	4.3	4.5	4
3	0.00	0	0	8.8	10.4	9.1
4	3.50	4.7	6.5	2.4	1	1.1
5	7.20	1.8	6.9	1.1	1.4	1.2
6	6.00	3.5	5.6	9.1	6.5	6.4

[izzy turner]

Hi, I have been struggling to find the best solution to measure intra rater reliability, and hope someone can help. I have used the ICC function as a two-way mixed analysis to look at whether there is reliability at a single timepoint, but this seems to relate to inter-rater reliability only. I am measuring the same x-ray angle three times(1-3) at five timepoints (t1-t5)
1, I would like to see if the measurements are reliable at a single time point, i.e. that the differences between the repeated measures are insignificant given the normal patient variation and
2, Whether for each patient the differences between the repeated measures are insignificant given their variation over time (I could just look at t1 and t5 for ease)
There's quite a bit of missing data which is at different timepoints for each observation, I have about 50 observations (nncode). The data is currently has the variables in the format below, although I'm aware I may need to change this to long and am happy to do that. Any assistance gratefully received.
observationid t1_1 t1_2 t1_3 t2_1 t2_2 t3_3