Based on the meaning of "testing something new":
* Routine: A regular, established way of doing something, the opposite of trying something new.
* Tradition: Something done in the same way for a long time, the opposite of innovation.
* Established practice: A method that has been proven effective and is widely accepted.
Based on the meaning of "trial and error":
* Certainty: Knowing something with complete confidence, the opposite of being unsure or testing.
* Prediction: Knowing something in advance, the opposite of needing to find out through testing.
Based on the meaning of "scientific experiment":
* Observation: Simply watching and recording, without manipulation or testing.
* Theory: An explanation or idea, but not a tested one.
Ultimately, the best antonym for "experiment" depends on the specific context in which you are using the word.
