What analysis is best for my research

Hi all,

I'm currently doing my masters thesis about blood pressure monitors.
I'm compairing them on repeatability using a simulator.

Now i have 5 different devices with each 3 simulations x 85 measurements. (Simulations are High blood pressure, low and normal)
I did the basic thing like look at the mean values and standard deviations but want to go further.

What I already tried to do:

I used excel to calculate this but the really really small;

Seems like I'm doing something wrong here.
Used my 2 columns in excel, two sided and coupled.. should be correct.

Bland Altman analysis;
Seems like my measurements are not different enough from one another to have a good analysis since i'm only getting 3 different points;


So my question to you guys is if somebody point me in the right direction on which analysis should be good for this research.
I've posted an example of my measurement of 1 device in attachement. (with no calculations on this one)

Thank you in advance!


The research question is:
What is the repeatability of the various commercially available blood pressure monitors.

For now I found the problem in my t-test in the upper message and i'm now having these kind of results;


Since the variance is liltle, my t-test doesn't give any good results.
For my research question these monitors are good (little variance) so I would need to use another type of test but I didn't find the right one yet.

Hope this makes it clearer, if not please let me know.