When you are testing your connection whilst connected with an Ethernet cable, you are more likely to get a more accurate result. This is because the internet signal is being guided directly from your modem to your laptop/PC.

When you connect via a wireless connection, the signal from your modem to your laptop/PC is directed through radio waves, which can interfere with other electronic components and as a result reduce your speed considerably.

You can always test out your connection using the MyGO feature any time you want.