Glicko.Player.rating_interval

You're seeing just the function rating_interval, go back to Glicko.Player module for more information.
Link to this function

rating_interval(player, as_version \\ nil)

Specs

rating_interval(player :: t(), as_version :: version() | nil) ::
  {rating_low :: float(), rating_high :: float()}

A convenience function for summarizing a player's strength as a 95% confidence interval.

The lowest value in the interval is the player's rating minus twice the RD, and the highest value is the player's rating plus twice the RD. The volatility measure does not appear in the calculation of this interval.

An example would be if a player's rating is 1850 and the RD is 50, the interval would range from 1750 to 1950. We would then say that we're 95% confident that the player's actual strength is between 1750 and 1950.

When a player has a low RD, the interval would be narrow, so that we would be 95% confident about a player’s strength being in a small interval of values.