Common Misreads of Performance Data (and How to Avoid Them)

List common mistakes when interpreting performance data, and how to avoid them when measuring Speed Layer.

Avoid using a single PageSpeed run as a success metric. Use trends and real user experience data.

Averages can hide poor experiences for a large group of users. Percentiles such as p75 are often more meaningful.

Homepage, SRP, and VDP behave differently. Track them separately.

Mobile performance often differs dramatically from desktop. Segment results.

Performance can change due to:

Track changes over time and isolate tests when possible.

A site is not successful if key tools fail. Validate lead tools and shopping flows alongside performance.