Whenever you take these tests you need to be asking yourself 1) am I improving? And 2)Am I ready to sit for the USMLE?
I strategically did mine in the order that would see if I was improving. 17 and UWSA1 should be done early because they are very easy compared to the others. And you should be able to match those scores on the harder NBMEs. Looking at your trend from these answers the first question. 13 and 15 are good to see question style from NBME but are not the most representative.
My order was:
13
17
UWSA1
15
19
UWSA2
18
17, 18, 19 and UWSA2 are most like the real deal. I did 19 before 18 because 19 has such a harsh curve.
UWSA2 and 18 should answer the question, am I ready to sit for the USMLE?