In my copy of the BW Codex in the Practical Magic section on pg 263 at the end of the 3rd paragraph it reads “The standard success and failure rules apply.”
What are those rules that apply? What does it mean to fail a Practical Magic test?
Practical Magic doesn’t have Spell Facets the way normal Sorcery does, so you can’t use the Wheel of Magic. Plus where normal Sorcery is flashy and powerful with various spells, Practical Magic is more muted…especially for the Ob listed for some of the tasks. Rip a hole in Reality and summon a deity when you fail the Ob 6 test to Appraise candles?
And as a side and semi-unrelated note, my group is house ruling PM to break up the Sorcery skill into each School of Magic. So performing Social magic advances the Social Sorcery skill while using magic to wield a hammer in battle advances the Martial Sorcery skill.