Interpretation
Compare wired results near the router with the subscribed service, then compare Wi-Fi in each important room. This separates provider speed from local wireless coverage.
Create a fair speed-test baseline
Use Ethernet to the primary router where possible, stop large downloads and test more than once. Record the server, time, latency, download and upload results. Then repeat over Wi‑Fi with the same client close to the router and at the problem location.
Interpret the difference
If Ethernet is also slow, investigate the ISP, modem/ONT, WAN negotiation or router processing. If Ethernet is healthy but Wi‑Fi is slow, examine band, channel conditions, distance, client capability and mesh backhaul. One unusually high or low result should not be treated as definitive.
Advertised Wi‑Fi class is not the same as Internet-plan speed or real application throughput.
Final verification step
For repeatable evidence, record the Ethernet link speed and the router port used. A 100 Mb/s negotiation, powerline adapter or older switch can cap results even when the broadband plan and router support much higher rates.