If you have the number of roundtrips and size of documents you can easily calculate page load speed dependent on latency, packet loss rate and connection speed.

If you have the number of roundtrips and size of documents you can easily calculate page load speed dependent on latency, packet loss rate and connection speed. That allows you to simulate nearly any connection in the world. Which is the reason why Google focuses so much on the number of roundtrips. For most, downloading 50kbyte doesn't cause a lag but 10 roundtrips before the site can be rendered do.