I think the tests are more directed towards the ability of someone to take information from your computer. It's not a test of anti-virus capability.should I consider changing to another anti-virus programme.
I have both my compuers behind a hardware firewall built into a router and so I get results much the same as Sonnie. No one gets in my door.
A router with its own DHCP server is the answer to shield your computer from the internet. I'm sure that the Norton you have running will protect against virus's though.