Every guide is written by Alex Reed and lists its sources at the foot of the page, with the date each was read. The calculators, the 31-model treadmill dataset and the diagrams are built in-house; lab results come from named laboratories such as Stiftung Warentest and Consumer Reports and are credited to them.
The calculators are models built on inputs you can see and change, not measurements of your room, and each one says so where it sits. How sources are graded and how corrections are handled is in the Editorial Policy, and the workings behind the tools and the dataset are in the Methodology. If you spot an error, contact us.