Line Quality / Speed

[#1]

I was curious a few days ago and decided to try a line tester from the following website: http://www.myconnectionpc.com/
The tests are a bit technical, but they do provide some explanations. However, I was surprised to find that the result for my connection kept failing some of their tests, notably the "Round trip time" test. Sometimes it was too high (circa 53 ms) and sometimes too low (about 17ms), but I could never get it to give a clean bill of health on all the tests. My question is, in reality, do tests such as these give meaningful results and also, what parameters for speed, jitter, round trip time, etc, should I be expecting for a FTTC line?

[#2]

I have never used the site in question, but would you say that you're experiencing any actual problems with your connection?
Presumably the "Round trip time" is your ping, which can be found on the BT Wholesale speed test too.