When you build custom charts in Favorites, you can select the "stat": median, average, or 75th/95th percentile. Sometimes changing the stat doesn't change the chart. This is normally because each point in the chart is coming from a single test. But why is that?
The stat setting controls how SpeedCurve aggregates the data for each point in the chart. When you build a chart that pulls in data from multiple sites, URLs, regions, or browsers, then each point in the chart will be the aggregate value of multiple tests. You can see how many tests have been aggregated by clicking on any point in the chart. This chart below is being aggregated over 6 tests:
Depending on your chart settings, it might be possible for a point to only be aggregated over 1 test. In this case, the stat will make no difference since the average of any single value is the same as the median, and the 95th percentile (and any other percentile, for that matter).