Does catchers interference factor into on base percentage?

No. On-base percentage is calculated by adding hits, walks and hit-by-pitches and dividing that number by the sum of all at-bats, walks, hit-by-pitches and sacrifice flies. (Source: www.homerunweb.com/onbase.html)

A fielder's choice does not improve a player's batting average, and neither does an error.

djagameking:

Actually an error counts towards your on base percentage, just not your average. Does a fielder's choice count towards your obp.